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Kestrel Wind tunnel data
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From Xtri, the new 4000 v P3C and other in the Kestrel/Fuji family.



Suffer Well.
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Re: Kestrel Wind tunnel data [jmhtx] [ In reply to ]
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Really? How can you tell if that it's true? This whole aero arms race makes me dizzy.

customerjon @gmail.com is where information happens.
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Re: Kestrel Wind tunnel data [Mr. Tibbs] [ In reply to ]
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Really? How can you tell if that it's true?
Well, you could use a powermeter to conduct some field tests, e.g., by riding laps around the velodrome in LA aboard a P3C or Fuji D6.
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Re: Kestrel Wind tunnel data [jmhtx] [ In reply to ]
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1) Why no P4?
2) If data was measured out to 30*, why is this data not reported?

That said... what wheels were used? I'd love to see a lot more information on this study before I declared it worthwhile at all.
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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Can I use the Superdrome in Frisco.

customerjon @gmail.com is where information happens.
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Re: Kestrel Wind tunnel data [Mr. Tibbs] [ In reply to ]
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Can I use the Superdrome in Frisco.
Absolutely. Just make sure to pick a really low wind morning (or evening).
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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I'm all over it. Will have the data up in a few hours.

customerjon @gmail.com is where information happens.
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Re: Kestrel Wind tunnel data [Mr. Tibbs] [ In reply to ]
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I'm all over it. Will have the data up in a few hours.

You've got a new 4000 at your disposal? Then by all means, go for it!

If you don't, then let me be the first to offer to field test one for Steve H/Kestrel... :-)
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Re: Kestrel Wind tunnel data [jmhtx] [ In reply to ]
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Well once again we see wind tunnel data that is in direct conflict with another. The cervelo data from last year when the P4 was released was not so nice to the Airfoil. And didn't some one say that the D-6 was the fastest bike in the world at 30 degrees? If so, why not include that.
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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Just finished. I look sexy on all bikes.

customerjon @gmail.com is where information happens.
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Re: Kestrel Wind tunnel data [cbritri] [ In reply to ]
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It says at the bottom "Complete bicycles were tested as they would be recieved by the customer"

I wonder which of the 3 Kestrel 4000s they tested? The $10,000 version with Zipps? Against the $4500 P3 with stock shimano wheels?

Definately need more info.

-Adam

http://www.austintricyclist.com
Facebook http://www.facebook.com/austintricyclist
Twitter: http://twitter.com/#!/ATCTriShop

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Re: Kestrel Wind tunnel data [persondude27] [ In reply to ]
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1) Why no P4?
2) If data was measured out to 30*, why is this data not reported?

That said... what wheels were used? I'd love to see a lot more information on this study before I declared it worthwhile at all.

I'm a bit surprised by these results - just because it's such a significant difference. With that said, I'm not really sure what they could've skewed here. Looking purely at P3 vs the 4000, as they fit similarly: aerobars, seats, wheels wouldn't seem to give one a significant advantage over the other.

Of course, they don't actually say whether they used the same wheels/bars/saddles/components on both bikes, or that the sizes were comparable, which could obviously skew the data (though it would be quite dishonest).

Also, according to cervelo's data, the P3 tests at ~700g of drag (0 yaw), the P4 at 575. cervelo also shows the P4 as worse at 10 yaw than 15, which kestrel doesn't. Kestrel has the P3 testing at 850g. Protocols can be skewed, but the final numbers can't, and the fact that cervelo could get 150g better than Kestrel definitely implies that the P3 was set up in some non-optimal way.
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Re: Kestrel Wind tunnel data [ATC] [ In reply to ]
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good points. Even ignoring wheels, the P3 comes stock with non-aero cranks, pretty low-end aluminum base bar upturned, and significantly upturned extensions, which would all test poorly. Anyone looking at buying any of the new high-end bikes would likely replace all of that anyway.
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Re: Kestrel Wind tunnel data [ATC] [ In reply to ]
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Well, since you guys can get all of the bikes tested...let's get them, go to TAMU with Mr. Cobb, and see which one is fastest. We can grab a Felt from down the street too. And we can probably get a TTX and Transition from down the street at the other place too.

Can we start a ST.com fund for the testing?


Brandon Marsh - Website | @BrandonMarshTX | RokaSports | 1stEndurance | ATC Bikeshop |
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Re: Kestrel Wind tunnel data [-Tex] [ In reply to ]
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Lets see what I have laying around:

Don's P4
George's P3
My E-114
Cannondale Slice

So we need A kestrel 4000, A Felt DA, and TTX.

Also I need around the clock security just in case one of these bike companies trys to stop us.

-Adam

http://www.austintricyclist.com
Facebook http://www.facebook.com/austintricyclist
Twitter: http://twitter.com/#!/ATCTriShop

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Re: Kestrel Wind tunnel data [ATC] [ In reply to ]
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You know, we could have this conversation over the phone. But, I am kind of serious.

I think that John has some tunnel time in November. If the ST brain trust (or forum junkies) were interested, and we could come up with some donations...it'd be a fun test.

Same bars and bar position, same seat height, clip off all the cables, same wheels, etc. and run them through the 0-15 (or whatever) yaw and be done with it.


Brandon Marsh - Website | @BrandonMarshTX | RokaSports | 1stEndurance | ATC Bikeshop |
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Re: Kestrel Wind tunnel data [-Tex] [ In reply to ]
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Same bars and bar position, same seat height, clip off all the cables, same wheels, etc. and run them through the 0-15 (or whatever) yaw and be done with it.
Although it would make things more expensive, I would advocate testing the bikes with cables in place - after all, many of the newer designs attempt to reduce drag by hiding/relocating the cables, such that leaving them off might bias the data.
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Re: Kestrel Wind tunnel data [-Tex] [ In reply to ]
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We have the bikes, the mechanics, and the time. All we need now are some funds....

http://www.austintricyclist.com
Facebook http://www.facebook.com/austintricyclist
Twitter: http://twitter.com/#!/ATCTriShop

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Re: Kestrel Wind tunnel data [ATC] [ In reply to ]
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It says at the bottom "Complete bicycles were tested as they would be recieved by the customer"

I wonder which of the 3 Kestrel 4000s they tested? The $10,000 version with Zipps? Against the $4500 P3 with stock shimano wheels?

Definately need more info.

-Adam

That was my first thought exactly when I read that part....sigh...I really hope that's not the case.

http://bikeblather.blogspot.com/
Last edited by: Tom A.: Oct 7, 09 16:35
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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You guys realize this is just marketing, right?
I mean, what company is going to come out and say "Hey, we'd like it if you buy our bikes, but really brands x, y, and z are all faster than ours".
It isn't about telling the truth, it's about selling a product.
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Re: Kestrel Wind tunnel data [ndenezzo] [ In reply to ]
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In Reply To:
You guys realize this is just marketing, right?
I mean, what company is going to come out and say "Hey, we'd like it if you buy our bikes, but really brands x, y, and z are all faster than ours".
It isn't about telling the truth, it's about selling a product.

Marketing is all well and good...but when wheels can be readily changed between framesets, and TT/Triathlon bikes are commonly sold with just "training wheels" (with the assumption that the buyer will be putting on his own race wheels), IF the test actually DID consist of testing the Kestrel with a deep Zipp wheelset vs. a P3 with a low profile wheelset, well that starts crossing the line into intentional obfuscation.

If you have a good product to sell, you don't need to stoop to such things to effectively sell it...

Did you notice that when Mark Cote revealed the tunnel data on the Shiv in comparison to the Transition (and previously Transition vs. P3) that the testing was done with the same wheelset between the bikes?

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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If you have a good product to sell, you don't need to stoop to such things to effectively sell it...

True, but I'm a cynical person by nature, and I don't really trust anything given by the company selling it.
Cervelo, Specialized, Giant, Trek, Kestrel, Felt, they all have "data" that proves their bike is faster than everybody else's. But someone must be doing something to skew the data, because they can't all have the "fastest" bike.
Same with Zipp vs HED vs Reynolds vs Blackwell, etc.
Everybody has data to prove their stuff is better than what the other guys are selling.
If there's data from an independent source, I'm much more likely to believe that than anything a company tells me. Sure, a good company should be honest, but selling products seems to come first.


EDIT: I'm not saying Kestrel did or didn't do anything shady here. I highly doubt they would have done something so drastic as use deep dish wheels on their bike, and box rims on the others. The cynic in me just thinks that any company will do small things to make their bike come out on top in testing.
Last edited by: ndenezzo: Oct 7, 09 17:25
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Re: Kestrel Wind tunnel data [ATC] [ In reply to ]
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"I wonder which of the 3 Kestrel 4000s they tested? The $10,000 version with Zipps? Against the $4500 P3 with stock shimano wheels?"

Ummmm...ok...yeah, they don't say specifically on this chart....but it would be a stretch to think Kestrel would jeapordize their reputation putting out data that would be roundly ridiculed and recognized as a poor effort at making their product falsely stand above other NAMED manufacturers. No reputable manufacturer is going to make such a blatant attempt in the days of internet gossip fires.

Also, IIRC Sharad has already posted details on the testing in some thread here...
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Re: Kestrel Wind tunnel data [-Tex] [ In reply to ]
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Can we start a ST.com fund for the testing?
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I'm in for $27.

Brian Stover
Accelerate3 Coaching
Insta Twitter Aero testing late May, PM for details

Last edited by: desert dude: Oct 7, 09 17:34
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Re: Kestrel Wind tunnel data [TriBriGuy] [ In reply to ]
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Also, IIRC Sharad has already posted details on the testing in some thread here...

Nope...but this was on xtri.com:

http://www.xtri.com/...p;CAT=21&xref=xx

Sounds to me like they DID test the P3 with the Shimano R-550 wheels. So, it remains to be seen which "level" of 4000 was tested against it, the LTD (which comes with an 808/1080 set) or the SL model (Ksyrium Elites).

BTW, I have to respectfully disagree with Mr. Harad that they have come up with "the standard on testing" in using bikes "as spec'd" for the testing. That would make sense if the buyers weren't allowed to switch wheels, bars, or saddles even when racing.

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [ndenezzo] [ In reply to ]
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"EDIT: I'm not saying Kestrel did or didn't do anything shady here. I highly doubt they would have done something so drastic as use deep dish wheels on their bike, and box rims on the others. The cynic in me just thinks that any company will do small things to make their bike come out on top in testing"

Well...for you cynics...I think you're trying to glean too much out of reported data. Given the design elements of this Kestrel, its entirely believable that this bike belongs in the same grouping as the P4, Shiv, etc....and that the apparent gap to the previous generation of bikes (of which the Fuji D6 belongs by virtue of its premier design elements)...is entirely believeable.

So you're probably safe in choosing the 4000 over a P3, just as the graph indicates.

However...even if you had the data from Kestrel of a P4, Shiv, etc...included in this graph...

You'd really have to take examples of those bikes set up specifically for you to a windtunnel to determine which might be faster.


For one thing, AC, Tom A., Steve Hed, John Cobb, and others have all said or at least concurred that comparing wind tunnel results from one event to another is VERY tough to do, if not just downright inadvisable given the numbers of variables that would have to be controlled for to equalize the data sets.

These companies all use many of the same facilities...which are open to whomever is willing to fork over the $ for time in the tunnel. No reputable company is going to risk their reputation in a low margin marketplace by reporting false data.

I guess what I'm trying to say is that most of us don't have the time or inclination of guys like Tom A., AC, etc...to go do in depth field testing. So the next option is to gather as much reported data as you can find...and look for trends. Right now, the trend is for the serious players to be producing bikes that are clearly going a step ahead of the P3C generation. Without paying for my own wind tunnel time with multiple frames...I can't say that the Kestrel is definitively among that group. But I think its a pretty safe move to believe the Kestrel data showing a break with the previous generation in this instance. On the other hand...if the data included a P4 and showed a similar break with that frame....I think we'd all be correct in raising the "Huh?" banner.

Don't let your cynicism lead you to inaction if you're looking for a new bike.

"The cynic in me just thinks that any company will do small things to make their bike come out on top in testing."

So my question is, given Kestrel's statement on the graph that the bikes were spec'd as sold, then if Kestrel's chosen front end configuration is tested more aerodynamic than Cervelo's...is Kestrel doing "small things to make their bike come out on top in testing? Or couldn't you also just say that Kestrel is being smart selling an all-around better piece of gear? In other words...maybe Kestrel is just trying to sell the consumer a better piece of equipment...and gaming the test data isn't the goal of the chosen tested specs. (I have no idea whether Kestrel's spec'd front end is better...just using it to illustrate the greater point).
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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"BTW, I have to respectfully disagree with Mr. Harad that they have come up with "the standard on testing" in using bikes "as spec'd" for the testing. That would make sense if the buyers weren't allowed to switch wheels, bars, or saddles even when racing. "

Yeah...I agree in principle. But I can see Kestrel's philosophy in that most P3s go out the door with Cervelo's spec'd front end on them. This will be the same for Kestrel 4000s...most buyers will not change out the spec'd item, at least initially. So if they want to use the saddle, bars, brake levers, shifters, components, etc. on the given spec...then fine by me, as long as you state that is the philosophy. On the other hand, many buyers will own race wheels other than the stock wheels on the bike. So it wouldn't really help the average buyer unless they standardize the wheels between the tested bikes to control them out of the data.

That won't satisfy the data dinks like you, Tom...but if I were a manufacturer...I wouldn't be targeting people like you with published data...at least not today in 2009...where the true aero geeks are going to do their own testing and analysis to make a more individual choice.

Is that marketing? I suppose it is in some respects.

Just conjecturing, to be sure, as I have no other data than anyone else here.
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Re: Kestrel Wind tunnel data [Andrew V] [ In reply to ]
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Even ignoring wheels, the P3 comes stock with non-aero cranks, pretty low-end aluminum base bar upturned, and significantly upturned extensions, which would all test poorly.

Cranks are not aero. Zipp made a full-on aero version and claimed 8 seconds in a 40K. That's a bit of a stretch.

pretty low-end aluminum base bar upturned, and significantly upturned extensions, which would all test poorly.

Don't kid yourself; the Vision base bar is the best bargain in tri. I've seen results where it equalled or exceeded another brand's flat bar with integrated brake levers. Vision's brake levers are designed to be used on the upturns and are angled accordingly. I've yet to see any prove that cutting off the upturns actually made them faster. The home jobs I've seen traded exposed surface area in one place for exposed surface area in another.

Chad
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Re: Kestrel Wind tunnel data [TriBriGuy] [ In reply to ]
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I think we all need more precision and info from the kestrel guy with pic of the configuration of each bike they tested.

I have no douth that if they really want to be open and honest about this test, they will show it to us. But for now...that test with those info given is worthless....

Jonathan Caron

Jonnyo Coaching
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Re: Kestrel Wind tunnel data [cdw] [ In reply to ]
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Cranks are not aero. Zipp made a full-on aero version and claimed 8 seconds in a 40K. That's a bit of a stretch.
Just as an FYI, it was 8 seconds over the next closest AERO crankset, which *I* *assume* was the FSA NeoPro. I don't know the data over say a SRAM Force crankset. Just the facts, ma'am.

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Kestrel Wind tunnel data [desert dude] [ In reply to ]
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"
Post: Can we start a ST.com fund for the testing?
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I'm in for $27. "



I wouldn't waste even that much money on generic testing. If you're totally invested in having the fastest bike, a little patience will turn up enough data to narrow the field down to just a few suspects. Then...

You can all just pitch in $10k for me to take my choices into a tunnel with a well-designed, transparent protocol...and I'll be happy to tell you which one tests fastest FOR ME! ;-)

Barring that...just write P4, 4000, Shiv, Speed Concept, Giant TT, Plasma 3...post them on a dart board...toss a dart...and be done with it.

The rest is in your legs.


PS....if you're paid to ride...none of this applies. Shut up and ride what they give ya! ;-)
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Re: Kestrel Wind tunnel data [desert dude] [ In reply to ]
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The $27 seems so arbitrary that I will have to second it, and volunteer another $27 for testing.
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Re: Kestrel Wind tunnel data [cdw] [ In reply to ]
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Chad

i agree, the vision tech is the best buy for your money. BUT to cut the upward part and put a good set of aero levers was a kick ass move aerowise. Not even close to the uncut version. I wonder what data you saw.....????

Jonathan Caron

Jonnyo Coaching
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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Sounds to me like they DID test the P3 with the Shimano R-550 wheels. So, it remains to be seen which "level" of 4000 was tested against it, the LTD (which comes with an 808/1080 set) or the SL model (Ksyrium Elites).

BTW, I have to respectfully disagree with Mr. Harad that they have come up with "the standard on testing" in using bikes "as spec'd" for the testing. That would make sense if the buyers weren't allowed to switch wheels, bars, or saddles even when racing.

While I agree that it's hard to fairly compare bikes using manufacturer tests, I think you can using the following assumptions:

1) The P3 in Cervelo's tunnel tests was set up in a favorable position.
2) The 4000 in Kestrel's tunnel tests was set up in a favorable position.
3) A company reporting ~675 grams of drag on a bike at 0 yaw did in fact manage to measure the bike under that much drag in some way.

Putting those facts together, it seems to be a reasonable assumption that the 4000 and P3 are similar bikes aerodynamically. Honestly, however, who cares? If you're looking at a 4000, you're looking at the P4, not the P3. If Kestrel wants their marketing to hold up here, and sell bikes off of it, they need to show it in a legitimately fair, well documented comparison with the P4.

If they want a fancy chart for dealers to use that will increase sales, they've done it.
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Re: Kestrel Wind tunnel data [Rappstar] [ In reply to ]
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Cranks are not aero. Zipp made a full-on aero version and claimed 8 seconds in a 40K. That's a bit of a stretch.
Just as an FYI, it was 8 seconds over the next closest AERO crankset, which *I* *assume* was the FSA NeoPro. I don't know the data over say a SRAM Force crankset. Just the facts, ma'am.

Cranks/chainrings are not wheels. Even so, 8 seconds over a 40k isn't remotely unreasonable compared to a decent crank, such as Dura-ace. There's ample opportunity for air to go turbulent through all those holes.

Ever looked closely at the FSA NeoPro? It's pretty, but it's not optimum. Eyeball wind tunnel says that the Zipp ones are faster. 8 seconds? Maybe, maybe not. Tough sell, since the data is unsupported from Zipp. Bottom line, I'm almost certain that the Zipps are faster (nobody else has even tried to compete), and I would be almost certain that they save over 8 seconds over a standard chainring; probably significnatly more.
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Re: Kestrel Wind tunnel data [Andrew V] [ In reply to ]
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We are getting a little off track on the Kestrel test, but I called Zipp when those came out and was told it was 8 seconds faster than the FSA Neo Pro, and 12 seconds faster than a "typical" non-aero crank. The test was done on a bike with rider pedaling.
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Re: Kestrel Wind tunnel data [jonnyo] [ In reply to ]
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BUT to cut the upward part and put a good set of aero levers was a kick ass move aerowise. Not even close to the uncut version.

Did you test that personally? The problem with home testing is that once you've cut them off, they are off.

Chad
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Re: Kestrel Wind tunnel data [cdw] [ In reply to ]
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no chad... i didnt test it myself. But i sure cut mine when i saw the test results ;)

Jonathan Caron

Jonnyo Coaching
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Re: Kestrel Wind tunnel data [TriBriGuy] [ In reply to ]
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Ok, so I may have exaggerated a little bit. I do trust the manufacturer data enough to place each bike into a specific category (in this case, the P4, Kestrel, Shiv, Giant, Trek SpeedConcept, etc. category).
My main thought was that, among the bikes listed, manufacturer data is useless in determining which is "fastest" within the category. (I think we're in agreement here, but I could be wrong. Wouldn't be the first time)
While the Kestrel most likely is a better choice than the P3, I'm skeptical that the size of the gap between the two is entirely accurate.
I'm not in the market for a new bike, but if I were, aero data would not be at the top of my list. I would be more focused on price, comfort, fit, etc.

And with regard to the "small changes" I was referring to in the testing, I didn't mean components so much as just the way the bike is set up. For example, leaving the cables a little bit longer on the competitor's bike, using an extra spacer or two, or testing without a seat (like another company did), or small things of that manner.
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Re: Kestrel Wind tunnel data [jonnyo] [ In reply to ]
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hmmm, I had been considering cutting mine soon. If it's as good as you say, I just might do it. Do you have the results for it?
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Re: Kestrel Wind tunnel data [jonnyo] [ In reply to ]
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Ahhh, so you have seen something definitive. Is it shareable? :) I have not and would have to be convinced it was significant before I gave up the safety of my upturns. On the other hand, if I had 12 bikes like you do, I'd have a race bike set up that way and keep the upturns on my training bars.

Chad
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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It will also matter which year P3C they tested... ie with the latest 3T fork?

That was a big difference.

I also believe that they did test with similar wheels, but then the marketing guys said: "we need to show "data" that maximizes the differences between us and the competition"

And this graph was developed.
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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Also, IIRC Sharad has already posted details on the testing in some thread here...

Nope...but this was on xtri.com:

http://www.xtri.com/...p;CAT=21&xref=xx

Sounds to me like they DID test the P3 with the Shimano R-550 wheels. So, it remains to be seen which "level" of 4000 was tested against it, the LTD (which comes with an 808/1080 set) or the SL model (Ksyrium Elites).

BTW, I have to respectfully disagree with Mr. Harad that they have come up with "the standard on testing" in using bikes "as spec'd" for the testing. That would make sense if the buyers weren't allowed to switch wheels, bars, or saddles even when racing.
That is sad...really, really, really sad. If you want to do a fair comparison then the only thing that should differ are proprietary components, e.g., it makes sense to test a Specialized Transition with its special brakes and compare those results to a Cervelo P3 with standard calipers. Otherwise, though, everything should be identical....
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
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In Reply To:
Also, IIRC Sharad has already posted details on the testing in some thread here...

Nope...but this was on xtri.com:

http://www.xtri.com/...p;CAT=21&xref=xx

Sounds to me like they DID test the P3 with the Shimano R-550 wheels. So, it remains to be seen which "level" of 4000 was tested against it, the LTD (which comes with an 808/1080 set) or the SL model (Ksyrium Elites).

BTW, I have to respectfully disagree with Mr. Harad that they have come up with "the standard on testing" in using bikes "as spec'd" for the testing. That would make sense if the buyers weren't allowed to switch wheels, bars, or saddles even when racing.
That is sad...really, really, really sad. If you want to do a fair comparison then the only thing that should differ are proprietary components, e.g., it makes sense to test a Specialized Transition with its special brakes and compare those results to a Cervelo P3 with standard calipers. Otherwise, though, everything should be identical....

FWIW Andy, as shown sans rider, this P3C tested at 689g at 0deg yaw in 2006 at LSWT

so, not sure what wheels they used to get it up to 850g


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Re: Kestrel Wind tunnel data [jmhtx] [ In reply to ]
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From the chart :

>>Complete bicycles as they would be received by the customer

So they take a stock P3 with training wheels and compare it to their top of the line bike with race wheels? If they did that I think the entire industry would think Kestrel management were a bunch of lying, cheating, deceptive opportunists. Time will tell.
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Re: Kestrel Wind tunnel data [gtingley] [ In reply to ]
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FWIW Andy, as shown sans rider, this P3C tested at 689g at 0deg yaw in 2006 at LSWT

so, not sure what wheels they used to get it up to 850g


Yeah, that makes sense as my wife's P3C track bike came in just a little below that at TAMU. It is smaller than your bike and the conditions weren't identical (e.g., we tested it with less aero bars and with pedals attached), but everything still says that the only way a P3C would have as much drag as Kestrel claims is if a parachute were attached. ;-)
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Re: Kestrel Wind tunnel data [gtingley] [ In reply to ]
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Maybe they ran the tunnel @33mph or so? I didn't see the tunnel speed listed there .. in any case this 'data' raises more questions than it answers ...

heck my old alu P3 tested out at around 850 g-f drag @30mph (untared). Full bars, cables, extension, cranks, brakes, pedals @0/180 ....
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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"the only way a P3C would have as much drag as Kestrel claims is if a parachute were attached."

Or...what might it also say about the A2 tunnel vs LSWT? (Serious question...based on some of your previous comments on tunnels and testing, I am curious what amount of the difference, if any, might you REASONABLY attribute to different facility, conditions, etc. Also because when I read the above, I hear that you don't feel the P3's number is reasonable even if Kestrel is guilty of testing a full-up 4000 against a stock, non-race wheel P3. Hard to determine the amount of hyperbole in your parachute! )
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Re: Kestrel Wind tunnel data [TriBriGuy] [ In reply to ]
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"the only way a P3C would have as much drag as Kestrel claims is if a parachute were attached."

Or...what might it also say about the A2 tunnel vs LSWT? (Serious question...based on some of your previous comments on tunnels and testing, I am curious what amount of the difference, if any, might you REASONABLY attribute to different facility, conditions, etc. Also because when I read the above, I hear that you don't feel the P3's number is reasonable even if Kestrel is guilty of testing a full-up 4000 against a stock, non-race wheel P3. Hard to determine the amount of hyperbole in your parachute! )

The only wind tunnel that I have ever been to is the one at Texas A&M, but my understanding is that the numbers from different facilities can differ. That said, I have heard nothing but good things about the A2 wind tunnel - in fact, others (I can't recall who) have mentioned that it is the LSWT that may be "outlier". In any case, I can't imagine that the differences between various tunnels is large enough to explain the apparent discrepancy in these data.

As for the parachute comment, that was indeed hyperbole, as based on both the magnitude of the difference and Steve H.'s comments in that interview the most logical explanation would seem to be that they did indeed compare the bikes with different wheels, etc.
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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A little birdie told me that "things were done very fairly to all bikes in the test. The Kestrel is quite impressive" This little birdie was very close to the action and impartial.


3 Months of Paradigm Shifting Swim Instruction for Cheap // Your Professional & Private “Critique my Fit”

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Quote Reply
Re: Kestrel Wind tunnel data [Dave Luscan] [ In reply to ]
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In Reply To:
A little birdie told me that "things were done very fairly to all bikes in the test. The Kestrel is quite impressive" This little birdie was very close to the action and impartial.

If this were the case, then why would they not release a detailed testing protocol? Failure to provide data is always a bad thing.
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Re: Kestrel Wind tunnel data [Andrew V] [ In reply to ]
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In Reply To:
If this were the case, then why would they not release a detailed testing protocol? Failure to provide data is always a bad thing.

steve h (sharad here) promised us at the show that they would publish the details and as TomA mentioned be as transparent as possible.

He did say he was looking forward to the st thread on the topic, so I assume he is watching this (hi steve!) and will chime in eventually...

G


greg
www.wattagetraining.com
Quote Reply
Re: Kestrel Wind tunnel data [Dave Luscan] [ In reply to ]
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In Reply To:
A little birdie told me that "things were done very fairly to all bikes in the test. The Kestrel is quite impressive" This little birdie was very close to the action and impartial.

Then how does one explain the extremely high drag for the P3? The only answer that really makes sense (and is consistent with both Steve H.'s interview and the description on the graphic from xtri.com) is that it was tested with stock wheels.

BTW, does anyone know if the 4000 is UCI legal? I've received conflicting opinions...
Quote Reply
Re: Kestrel Wind tunnel data [Dave Luscan] [ In reply to ]
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In Reply To:
A little birdie told me that "things were done very fairly to all bikes in the test. The Kestrel is quite impressive" This little birdie was very close to the action and impartial.

But . . . but . . . but . . . Dr. Coggan implied otherwise!?!
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Re: Kestrel Wind tunnel data [Dave Luscan] [ In reply to ]
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""things were done very fairly to all bikes in the test"

Fairly is a relative term, depending on the philosphy used during the testing. Most companies are controlling out the non-proprietary gear to the greatest extent possible. In the absence of information about the specific setups on the bikes in the graph, and given the statement about essentially stock bikes, Kestrel appears to have changed that philosophy to be able to say "Look, the bike we give you at our MSRP is faster than the bikes these others give you at their MSRPs." (I'm still holding out that even if they took that tack, they would at least control out the wheels since those are the most likely suspects to be changed out by consumers in a race situation...and since, as others have noted, deep aero wheels vs stock aluminum clincher wheels leads directly to complete non-sequitur with this data set).

If that is, in fact, the case, as a consumer, I can appreciate that approach...even if the engineer in me wants to crawl down into the weeds and demand a complete apples-to-apples approach, since I'm unlikely to buy a stock bike anyway. I mean...take a look at any P3-infested transition area. By and large what you'll find are stock P3s with some Zipps, Heds or somesuch for wheels. Same with Spec transitions, Felt DAs, etc. So apparently, the average consumer isn't inclined to take the time to dig into each and every part of a bike's setup to determine the efficacy of the system. All they are concerned with is which of the bikes is going to be faster when they stick their Zipp 808s on it. That involves the entire system, not just the frame and proprietary fork, seatpost, headset, and/or stem.

Just a loose thought train... while I take a break from the engineering weeds here at work! ;-)
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Re: Kestrel Wind tunnel data [ndenezzo] [ In reply to ]
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In Reply To:
Ok, so I may have exaggerated a little bit. I do trust the manufacturer data enough to place each bike into a specific category (in this case, the P4, Kestrel, Shiv, Giant, Trek SpeedConcept, etc. category).


Ummm...I don't know if I'd place the 4000 into that "upper tier" just yet, especially based on that chart...since none of the others were represented and it's unknown what wheels were on the P3.

In any case, people are losing sight of some other bikes on there and how the data can be placed in context. For example, the Airfoil Pro "as recieved/tested" has values that are VERY similar to those shown for that bike in the Cervelo data that was assumedly run with deep wheels on the bikes (we know at least the airfoil had a rear disc). In that case there's an ~80gf difference at zero yaw between the Airfoil Pro and the P3. Judging by THAT, from what we know now (and making the reasonable assumption that the P3 in the Kestrel test was run with Shimano R-550 wheels) I'd put the 4000 more in the P3, P2, DA, TTX, Transition "tier" of bikes...which actually matches my "gut feel" of where it would fall when looking at the frame in person.

So...I'm going to go out on a limb here and guess which models of each bike were tested by Kestrel:

2009 P3
2010 Kestrel 4000 LTD
2010 Fuji D-6 RC Matt Reed Edition
Kestrel Airfoil Pro Special Edition

We'll see how well that matches up when (and if) that info is finally revealed ;-)

http://bikeblather.blogspot.com/
Quote Reply
Re: Kestrel Wind tunnel data [TriBriGuy] [ In reply to ]
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In Reply To:
""things were done very fairly to all bikes in the test"

Fairly is a relative term, depending on the philosphy used during the testing. Most companies are controlling out the non-proprietary gear to the greatest extent possible. In the absence of information about the specific setups on the bikes in the graph, and given the statement about essentially stock bikes, Kestrel appears to have changed that philosophy to be able to say "Look, the bike we give you at our MSRP is faster than the bikes these others give you at their MSRPs."

Assuming (always a dangerous thing) that was indeed their thinking and how the bikes were tested, then it would also only be fair to list the MSRPs:

Kestrel 4000 LTD: $10829
Cervelo P3: either $3600 or $4500 depending on spec

So IOW, you could buy two Ultegra-equipped P3s and a set of Zipp race wheels for the price of the Kestrel, have one bike for training and one just for racing, and likely not give up anything in the aero drag department...
Last edited by: Andrew Coggan: Oct 8, 09 7:44
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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You've seen a 4000 in person, Tom?
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Re: Kestrel Wind tunnel data [TriBriGuy] [ In reply to ]
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In Reply To:
You've seen a 4000 in person, Tom?

Yup...touched it too...while I was standing next to, and conversing with, Steve Harad :-)

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [hgrong] [ In reply to ]
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In Reply To:
In Reply To:
A little birdie told me that "things were done very fairly to all bikes in the test. The Kestrel is quite impressive" This little birdie was very close to the action and impartial.

But . . . but . . . but . . . Dr. Coggan implied otherwise!?!

It was actually ATC who first suggested that perhaps the bikes weren't fitted with the same wheels:

http://forum.slowtwitch.com/...post=2534689#2534689

All I've said is that explanation makes sense given the high drag for the P3, the statements on the original graph, and Steve Harad's interview on xtri.com. If there is some other logical explanation, then I'm all ears...
Quote Reply
Re: Kestrel Wind tunnel data [Dave Luscan] [ In reply to ]
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In Reply To:
A little birdie told me that "things were done very fairly to all bikes in the test. The Kestrel is quite impressive" This little birdie was very close to the action and impartial.

I guess that all depends on your (or the birdie's) definition of "fair"...

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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In Reply To:
You've seen a 4000 in person, Tom?

Yup...touched it too...
Ah, so that explains it - should we start calling you Midas now? ;-)
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
You've seen a 4000 in person, Tom?

Yup...touched it too...
Ah, so that explains it - should we start calling you Midas now? ;-)

Trust me, if you see how most of my projects around my house have been turning out lately...you'd start calling me the "anti-Midas" :-)

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
In Reply To:
You've seen a 4000 in person, Tom?

Yup...touched it too...
Ah, so that explains it - should we start calling you Midas now? ;-)

Trust me, if you see how most of my projects around my house have been turning out lately...you'd start calling me the "anti-Midas" :-)
Everything has been turning into lead, eh? ;-)
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Re: Kestrel Wind tunnel data [gregclimbs] [ In reply to ]
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In Reply To:
In Reply To:
If this were the case, then why would they not release a detailed testing protocol? Failure to provide data is always a bad thing.

steve h (sharad here) promised us at the show that they would publish the details and as TomA mentioned be as transparent as possible.

He did say he was looking forward to the st thread on the topic, so I assume he is watching this (hi steve!) and will chime in eventually...

G

Yeah...he DID say he somewhat enjoyed spinning up us "propeller heads" a bit, didn't he? Hi STEVE! :-P

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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In Reply To:
I'm going to go out on a limb here and guess which models of each bike were tested by Kestrel:

2009 P3
2010 Kestrel 4000 LTD
2010 Fuji D-6 RC Matt Reed Edition

Doesn't that version of the Fuji come with high-zoot aero wheels? Based on the data, I'd expect it to have been tested with wheels similar to those on the P3.
Quote Reply
Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
In Reply To:
I'm going to go out on a limb here and guess which models of each bike were tested by Kestrel:

2009 P3
2010 Kestrel 4000 LTD
2010 Fuji D-6 RC Matt Reed Edition

Doesn't that version of the Fuji come with high-zoot aero wheels? Based on the data, I'd expect it to have been tested with wheels similar to those on the P3.

Yup...1080s...that's why I guessed that one. Has any other data you've seen on the D6 been "bike only" (like apparently this data is)?

http://bikeblather.blogspot.com/
Quote Reply
Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
I'm going to go out on a limb here and guess which models of each bike were tested by Kestrel:

2009 P3
2010 Kestrel 4000 LTD
2010 Fuji D-6 RC Matt Reed Edition

Doesn't that version of the Fuji come with high-zoot aero wheels? Based on the data, I'd expect it to have been tested with wheels similar to those on the P3.

Yup...1080s...that's why I guessed that one. Has any other data you've seen on the D6 been "bike only" (like apparently this data is)?
So you're saying that you think a Fuji D-6 needs to be fitted with Zipp 1080 wheels to match the drag of a Cervelo P3 fitted with Shimano R-550 wheels? I haven't seen any bike-only data to suggest otherwise, but still...
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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There is absolutely no way that they bikes were tested with different wheels. It IS entirely possible that they were tested with the wheels that made the Kestrel bicycles look the best, but surely they were identical across the 4 models.

On the topic of the Cervelo data on the P3 vs Airfoil, I suspect that was done with the 2008 model of Airfoil, so the only constant between this new test and the Cervelo data is the P3 itself. Unfortunately that hasn't left us with much to go on.

Chris
Quote Reply
Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
In Reply To:
I'm going to go out on a limb here and guess which models of each bike were tested by Kestrel:

2009 P3
2010 Kestrel 4000 LTD
2010 Fuji D-6 RC Matt Reed Edition

Doesn't that version of the Fuji come with high-zoot aero wheels? Based on the data, I'd expect it to have been tested with wheels similar to those on the P3.

Yup...1080s...that's why I guessed that one. Has any other data you've seen on the D6 been "bike only" (like apparently this data is)?
So you're saying that you think a Fuji D-6 needs to be fitted with Zipp 1080 wheels to match the drag of a Cervelo P3 fitted with Shimano R-550 wheels? I haven't seen any bike-only data to suggest otherwise, but still...

Judging by the width of that seat tube/brake area, along with the "truncated" back half...oh, and also that silly behind the fork brake (with the attendant brake housing hanging out in the breeze)...well, yeah...let's just say I wouldn't expect it to be close to a P3C with the SAME "low line" wheels on both ;-)

http://bikeblather.blogspot.com/
Quote Reply
Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
In Reply To:
A little birdie told me that "things were done very fairly to all bikes in the test. The Kestrel is quite impressive" This little birdie was very close to the action and impartial.

Then how does one explain the extremely high drag for the P3? The only answer that really makes sense (and is consistent with both Steve H.'s interview and the description on the graphic from xtri.com) is that it was tested with stock wheels.

BTW, does anyone know if the 4000 is UCI legal? I've received conflicting opinions...
I don't understand the gripe here. They put on the graph that they tested the bikes as they would be delivered to the consumer. This would imply stock wheels for all the bikes. This seems like a fair test when directed to the consumer who isn't interested in and doesn't want to spend a couple of thousand more bucks after receiving the bike in order to make it even faster (probably the majority of them, none of whom hang out here).

--------------
Frank,
An original Ironman and the Inventor of PowerCranks
Quote Reply
Re: Kestrel Wind tunnel data [chicanery] [ In reply to ]
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There is absolutely no way that they bikes were tested with different wheels. It IS entirely possible that they were tested with the wheels that made the Kestrel bicycles look the best, but surely they were identical across the 4 models.

Ummm...how do you square your opinion with this quote from Steve Harad (bold added)?

Quote:
Well, we are going to put the wind tunnel data out shortly and Xtri will get the information right after Interbike.. Just know that we not only tested 20% faster then the Cervelo P3 and we also believe we have come up with the standard on testing. The concept is that I want to test bike vs. bike. Exactly how the consumer gets it. No cheating. It is helpful to the consumer to see what the bike on the floor of the bike shop tests, not just the frame or a partially assembled bike.

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
In Reply To:
In Reply To:
I'm going to go out on a limb here and guess which models of each bike were tested by Kestrel:

2009 P3
2010 Kestrel 4000 LTD
2010 Fuji D-6 RC Matt Reed Edition

Doesn't that version of the Fuji come with high-zoot aero wheels? Based on the data, I'd expect it to have been tested with wheels similar to those on the P3.

Yup...1080s...that's why I guessed that one. Has any other data you've seen on the D6 been "bike only" (like apparently this data is)?
So you're saying that you think a Fuji D-6 needs to be fitted with Zipp 1080 wheels to match the drag of a Cervelo P3 fitted with Shimano R-550 wheels? I haven't seen any bike-only data to suggest otherwise, but still...

Judging by the width of that seat tube/brake area, along with the "truncated" back half...oh, and also that silly behind the fork brake (with the attendant brake housing hanging out in the breeze)...well, yeah...let's just say I wouldn't expect it to be close to a P3C with the SAME "low line" wheels on both ;-)
How about the same "high zoot" wheels and a rider aboard?
Quote Reply
Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
BTW, does anyone know if the 4000 is UCI legal? I've received conflicting opinions...

Before or after bikes get shipped to Rwanda? ;-)

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
In Reply To:
In Reply To:
In Reply To:
I'm going to go out on a limb here and guess which models of each bike were tested by Kestrel:

2009 P3
2010 Kestrel 4000 LTD
2010 Fuji D-6 RC Matt Reed Edition

Doesn't that version of the Fuji come with high-zoot aero wheels? Based on the data, I'd expect it to have been tested with wheels similar to those on the P3.

Yup...1080s...that's why I guessed that one. Has any other data you've seen on the D6 been "bike only" (like apparently this data is)?
So you're saying that you think a Fuji D-6 needs to be fitted with Zipp 1080 wheels to match the drag of a Cervelo P3 fitted with Shimano R-550 wheels? I haven't seen any bike-only data to suggest otherwise, but still...

Judging by the width of that seat tube/brake area, along with the "truncated" back half...oh, and also that silly behind the fork brake (with the attendant brake housing hanging out in the breeze)...well, yeah...let's just say I wouldn't expect it to be close to a P3C with the SAME "low line" wheels on both ;-)
How about the same "high zoot" wheels and a rider aboard?

Then...all bets are off...

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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I would wager that he's talking about full cable routing and standard aerobars, not wheels.
Which brings up the point that certain aerobars definitely have more frontal area than others and could easily hose the whole result set.

Steven has been around enough of the aero conversations here to know not to test with different wheels. He would not have released that data no matter how great it showed his bikes to be. The credibility loss around here would be debilitating.

Chris
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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In Reply To:
this quote from Steve Harad (bold added)?

Quote:
Exactly how the consumer gets it.

...which in the case of the Kestrel 4000 Ltd includes not only race wheels, but also the super-slippery 3T Ventus aerobars. Considering how it is equipped (and how it is priced!), it darn well better be fast...
Quote Reply
Re: Kestrel Wind tunnel data [chicanery] [ In reply to ]
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In Reply To:
I would wager that he's talking about full cable routing and standard aerobars, not wheels.
Which brings up the point that certain aerobars definitely have more frontal area than others and could easily hose the whole result set.

Steven has been around enough of the aero conversations here to know not to test with different wheels. He would not have released that data no matter how great it showed his bikes to be. The credibility loss around here would be debilitating.

Chris

Well then...I (and others) will patiently wait for more transparency on the subject of what wheels were used...

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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It would indeed be a mistake for Steven not to show up and lay out the protocol now that the data has been "released", with specifics on equipment used for all 4 frames.

Chris
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
this quote from Steve Harad (bold added)?

Quote:
Exactly how the consumer gets it.

...which in the case of the Kestrel 4000 Ltd includes not only race wheels, but also the super-slippery 3T Ventus aerobars. Considering how it is equipped (and how it is priced!), it darn well better be fast...

Yeah...I wonder how it would test against a P4 DA Team edition (MSRP $12,500) with it's 1080 front and 900 disc rear? :-)

http://bikeblather.blogspot.com/
Quote Reply
Re: Kestrel Wind tunnel data [Dave Luscan] [ In reply to ]
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In Reply To:
A little birdie told me that "things were done very fairly to all bikes in the test. The Kestrel is quite impressive" This little birdie was very close to the action and impartial.

Would this little birdie understand aerodynamics? It's quite easy for a bike to be configured to look aero without actually being aero.

Also, I've been wondering about ways in which manufacturers could take a competitors bike, outfit it with the same kit as their own and end up skewing the results. The example I came up with was fitting a non-rotating tri-spoke with the blade sitting between the fork legs.
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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I wonder how it would test against a P4 DA Team edition (MSRP $12,500) with it's 1080 front and 900 disc rear? :-)

The Kestrel 4000 Ltd and the P4 Team Edition make that $1800 Specialized Transition Pro frameset look like a screaming deal, don't they? :-) If only I could get low enough on one...
Quote Reply
Re: Kestrel Wind tunnel data [zebragonzo] [ In reply to ]
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In Reply To:
I've been wondering about ways in which manufacturers could take a competitors bike, outfit it with the same kit as their own and end up skewing the results. The example I came up with was fitting a non-rotating tri-spoke with the blade sitting between the fork legs.




1a. You could leave the cables extra-long on a bike where they enter the sides of the downtube and compare it to a bike with neatly-trimmed behind-the-stem cable routing.

1b. You could leave the cables off entirely when comparing bikes that differ significantly in their cable routing.

2. You could test with the crank arms in different positions.

3. You could have the bar-end shift levers positioned differently.

Etc.
Last edited by: Andrew Coggan: Oct 8, 09 9:50
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
I wonder how it would test against a P4 DA Team edition (MSRP $12,500) with it's 1080 front and 900 disc rear? :-)

The Kestrel 4000 Ltd and the P4 Team Edition make that $1800 Specialized Transition Pro frameset look like a screaming deal, don't they? :-) If only I could get low enough on one...

Just use shorter cranks...or a slightly down-angled stem (that would "shield" the front brake cable stop anyway) ;-)

Yeah...the price on the Transition Pro frameset is sweet...especially considering I wouldn't pay MSRP due to my team sponsorship :-)

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
In Reply To:
I wonder how it would test against a P4 DA Team edition (MSRP $12,500) with it's 1080 front and 900 disc rear? :-)

The Kestrel 4000 Ltd and the P4 Team Edition make that $1800 Specialized Transition Pro frameset look like a screaming deal, don't they? :-) If only I could get low enough on one...

Can wheels attribute to all or most of of the differences?

Off the cuff, I estimate that an "aero-detailed" size 56 P4 with DA7900/1080/900disc/ventus would test in the low 600g* range.

(*based on numbers from other tests I have seen on the P3C, and the ~50-80g difference between the P3 and P4)

HED wheel data http://www.hedcycling.com/...dynamics_technology/

Difference between 808clincher and alloy oem wheel = 50g @ 0deg yaw (one wheel)

850g P3C KES test (unknown size/bar/wheels)
689g P3C 2006 test (56cm, HED bars/disc clincher/808 clincher)
----
161g

ROT = 50g = 20sec/40k/1hr

161g = ~1min difference over 40k/1hr between tests, on the same model P3C
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Re: Kestrel Wind tunnel data [gtingley] [ In reply to ]
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So perhaps if Disraeli were a triathlete he would have said "lies, damn lies and wind tunnel data."

Suffer Well.
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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In Reply To:
In Reply To:
The Kestrel 4000 Ltd and the P4 Team Edition make that $1800 Specialized Transition Pro frameset look like a screaming deal, don't they? :-) If only I could get low enough on one...

Just use shorter cranks...or a slightly down-angled stem (that would "shield" the front brake cable stop anyway) ;-)


Unfortunately, I don't think that either approach would solve the problem. I use a down-angled stem even on a 51 cm P3, which has a stack of 482 mm and a reach of 405 mm. The XS Transition has a similar stack of 487 mm, but 40 (!) mm less reach. If I go up a size or three, the reach becomes better, but then I'd need a markedly down-angled stem to get low enough (and would probably run into interference between the stem and the cable stop).

Of course, a Look Ergostem would solve the problem, but seems a bit of a kludge when you're spending so much $$ on a bike...


In Reply To:
Yeah...the price on the Transition Pro frameset is sweet...especially considering I wouldn't pay MSRP due to my team sponsorship :-)

One of the reasons I brought it up...don't feel too special, though: I'm friends with the guy who owns the local Specialized Concept Store. :-)
Quote Reply
Re: Kestrel Wind tunnel data [TriBriGuy] [ In reply to ]
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Your thinking right, as always, but my big question is how much of a time difference there is. Drag numbers are all cool and such but how much "slower" is one super bike from the next? It seems once you get into the level of 4000s, Shivs or P4s fit and feel are more important then numbers. I mean if the P4 is faster then the 4000 by a few seconds but I really dig the 4000 doesn't that count? Thoughts?

customerjon @gmail.com is where information happens.
Quote Reply
Re: Kestrel Wind tunnel data [Mr. Tibbs] [ In reply to ]
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In Reply To:
Your thinking right, as always, but my big question is how much of a time difference there is. Drag numbers are all cool and such but how much "slower" is one super bike from the next? It seems once you get into the level of 4000s, Shivs or P4s fit and feel are more important then numbers. I mean if the P4 is faster then the 4000 by a few seconds but I really dig the 4000 doesn't that count? Thoughts?

I haven't seen anything yet to put the 4000 into that same "tier" (Shiv, P4, etc.)...and that means that it could be slower over 40K by a lot more than just a "few seconds"...

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [chicanery] [ In reply to ]
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In Reply To:
It would indeed be a mistake for Steven not to show up and lay out the protocol now that the data has been "released", with specifics on equipment used for all 4 frames.

<sound of crickets chirping>
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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Data?

customerjon @gmail.com is where information happens.
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Re: Kestrel Wind tunnel data [Mr. Tibbs] [ In reply to ]
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In Reply To:
Data?

Data for what?
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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"I haven't seen anything yet to put the 4000 into that same "tier" (Shiv, P4, etc.)...and that means that it could be slower over 40K by a lot more than just a "few seconds"... "

The Slowtwitch Windtunnels ability to make big claims without data.

customerjon @gmail.com is where information happens.
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Re: Kestrel Wind tunnel data [Mr. Tibbs] [ In reply to ]
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In Reply To:
"I haven't seen anything yet to put the 4000 into that same "tier" (Shiv, P4, etc.)...and that means that it could be slower over 40K by a lot more than just a "few seconds"... "

The Slowtwitch Windtunnels ability to make big claims without data.

I'm confused - didn't Tom A. write that he hasn't seen any data that would make the 4000 the equal of the P4, Shiv, etc.??
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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He hasn't seen any data would make it unequal.

customerjon @gmail.com is where information happens.
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Re: Kestrel Wind tunnel data [Mr. Tibbs] [ In reply to ]
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In Reply To:
He hasn't seen any data would make it unequal.

And you haven't seen any data to indicate that they are equal - but that didn't seem to stop you from asserting that they are.
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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The point of the orginal post that started this side bar was not that the 4000 was as fast as the P4 but the excitment factor in bike selection. I don't know how the 4000 compares to the P4.

customerjon @gmail.com is where information happens.
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Re: Kestrel Wind tunnel data [gtingley] [ In reply to ]
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In Reply To:
HED wheel data http://www.hedcycling.com/...dynamics_technology/

Difference between 808clincher and alloy oem wheel = 50g @ 0deg yaw (one wheel)

x1.3 (2 wheels, but the back one is only about 1/3 as effective) and then add some because the HED drag data shows higher drag for Zipp wheels than any other source.
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Re: Kestrel Wind tunnel data [Mr. Tibbs] [ In reply to ]
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when the slowtwitch wind tunnel is the sum of AC and TA its pretty good

whens TD, or I, gets involved, look out!


In Reply To:
"I haven't seen anything yet to put the 4000 into that same "tier" (Shiv, P4, etc.)...and that means that it could be slower over 40K by a lot more than just a "few seconds"... "

The Slowtwitch Windtunnels ability to make big claims without data.



Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter
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Re: Kestrel Wind tunnel data [Mr. Tibbs] [ In reply to ]
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In Reply To:
Data?

Huh? You're the one that placed it at the same level as a Shiv, P4, etc.

I was just pointing out that there so far IS NOT any data that shows it actually could be at that level, and so your premise in your question is perhaps a bit premature.

And you're accusing ME of jumping to conclusions?? Nice...

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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Hey all,

Not sure when the data's from, but I figured I'd add a couple of points that might or might not be useful.

1. Upturned verus flat hand holds on aerobar basebars: We designed, built, and tested both for Saxo when making the Shiv. We tested at 0 and -15 degrees. The flat hand hold bar on the fully built bike (-tare) was 502 gF at 0 degrees and 389 gF at -15 degrees. The angled hand holds were worse by 7 gF at 0 degrees (509 gF) and better at -15 degrees by 21 gF (368 gF).

We since have finished an extensive study at A2 testing the same exact control bike over 6 months of testing -- full yaw sweeps of the exact same bike tested ~1 month apart at the same tunnel, same protocol. At 0 degrees, the data over 6 months is within 9 gF. At -15 degrees, the data is within 35 gF (more vortex shedding, component of side force load cell, etc -- we should expect data at yaw to be worse than 0 deg).

So -- TAKEAWAY -- same shape, design of basebar with only the upturn changing, the drag difference is almost immeasurable. So, we've gone with the upturned hand holds as you simply don't crash when going down hills/hitting bumps! Confidence in handling with aero performance is key.


2. Note that the tare values at A2 are about 180 to 150 to 180 gF across -25 to 0 to 25 degrees.

3. Kestrel's Cervelo data seems high to me but the trends seem to indicate the same wheels were used between the Kestrel and the Cervelo. I'd assume tares have not been subtracted. Looks like bar spec could be significantly different though. I'll wait to hear more because the data's confusing to me too.

Thought the bar stuff might be interesting though.

Cheers,

Mark

--
Mark Cote
MITAerobike
Specialized Bicycle Components
Quote Reply
Re: Kestrel Wind tunnel data [MITaerobike] [ In reply to ]
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In Reply To:
502 gF at 0 degrees and 389 gF at -15 degrees.

I'm still blown away by these reported numbers...

Anything you can share re. the UCI legality of the Shiv?
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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They're real. Still waiting to hear from the UCI but no matter what, we're planning to support the technology.

MC

--
Mark Cote
MITAerobike
Specialized Bicycle Components
Quote Reply
Re: Kestrel Wind tunnel data [MITaerobike] [ In reply to ]
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In Reply To:
Still waiting to hear from the UCI but no matter what, we're planning to support the technology.

So assuming that the UCI doesn't rule the bike illegal, what would it take for somebody like me to lay their hands on one? :-)
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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Re: Kestrel Wind tunnel data [jackmott] [ In reply to ]
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You realize that can be done by virtually anyone with just a bit of ingenuity and a few hundred hours to spare, right?

Chris
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Re: Kestrel Wind tunnel data [chicanery] [ In reply to ]
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In Reply To:
You realize that can be done by virtually anyone with just a bit of ingenuity and a few hundred hours to spare, right?

It's not just about making something that /looks/ aero!
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Re: Kestrel Wind tunnel data [zebragonzo] [ In reply to ]
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Yeah, shaping a nose cone is SO complicated. No reason not to do the CFD and publish the shape yourself.

Chris
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Re: Kestrel Wind tunnel data [MITaerobike] [ In reply to ]
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In Reply To:
In Reply To:
They're real. Still waiting to hear from the UCI but no matter what, we're planning to support the technology.

So assuming that the UCI doesn't rule the bike illegal, what would it take for somebody like me to lay their hands on one? :-)

Assuming they do anyway...and since you're planning on supporting the technology...either way, what would it take for somebody like me to lay their hands on one? :-)


BTW, you were supposed to respond "They're real...and they're SPECTACULAR!" :-)

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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Does this mean I need to sell my P3C? But I really like it!

Nevertheless, I always wonder how much wind tunnel data is "massaged" by the manufacturer to make their bike look better. I guess I'm a little skeptical about everything lately...
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Re: Kestrel Wind tunnel data [djarecke] [ In reply to ]
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The first Shivs will be available this spring. The nosecone was a very non-trivial development that actually did take a lot of CFD, layup, design, manufacturing time, and really only works well aerodynamically if there's no gap between the stem and the HT.

But I didn't come on here to hi-jack the thread -- just to make a note about the data and some basebar aero. I'm glad to see Kestrel kickin' out some new product and doing these studies throughout their development. Anyone with the company that can give us all a bit more info on the data, protocol, etc, please share.

Cheers,

MC

--
Mark Cote
MITAerobike
Specialized Bicycle Components
Quote Reply
Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
In Reply To:
502 gF at 0 degrees and 389 gF at -15 degrees.

I'm still blown away by these reported numbers...

Anything you can share re. the UCI legality of the Shiv?
Andy- why are you blown away from data from... A2... i thought you ripped me a new one for being an early tester there- and saying they had a really nice facility? Looks like Specialized is camping out there, along with Kestrel, Blue, Columbia, etc... :)
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Re: Kestrel Wind tunnel data [MITaerobike] [ In reply to ]
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I am curious about this concept. I realize that the MOST will be gained with a level top tube/stem interface, but is it really all that poor for a standard bolt on stem to lengthen the leading edge a bit? My testing (not exactly a wind tunnel) has shown that it's very awesome (though I don't know how much better it could be) despite not being level.

Thanks for any input.

Chris
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Re: Kestrel Wind tunnel data [chicanery] [ In reply to ]
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I don't think I understand the question. Is a stem being in line with the top tube good or the stem lengthening the airfoil section of the HT? Are you asking on of these?

MC

--
Mark Cote
MITAerobike
Specialized Bicycle Components
Quote Reply
Re: Kestrel Wind tunnel data [MITaerobike] [ In reply to ]
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In Reply To:
The nosecone was a very non-trivial development that actually did take a lot of CFD, layup, design, manufacturing time, and really only works well aerodynamically if there's no gap between the stem and the HT.

Does the nosecone not need to pass the credit-card test?
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Re: Kestrel Wind tunnel data [mlinenb] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
502 gF at 0 degrees and 389 gF at -15 degrees.

I'm still blown away by these reported numbers...

Anything you can share re. the UCI legality of the Shiv?
Andy- why are you blown away

Because of how low the numbers are. If correct, somebody on a Shiv would have a massive advantage over everybody else.

In Reply To:
from data from... A2... i thought you ripped me a new one for being an early tester there- and saying they had a really nice facility?

If you are referring to this thread:

http://forum.slowtwitch.com/...post=1676566#1676566

then I would say that your memory is quite faulty.
Last edited by: Andrew Coggan: Oct 9, 09 7:54
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Re: Kestrel Wind tunnel data [MITaerobike] [ In reply to ]
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The question is "how effective is the nosecone when it's NOT even with the head tube?" and/or "Is it worth having a nosecone when it's NOT even with the head tube?".

Chris
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Re: Kestrel Wind tunnel data [chicanery] [ In reply to ]
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Gotcha -- well there are things you can do to make a leading edge system like a bayonet work but it's pretty hard as the airflow trips across the gap. If the width of your leading edge piece is wider than your HT, then your wake region begins, you get some reattachment but not much at the Reynolds numbers we're working with.

Re number on at HT at 30 mph is still only 50,000 max -- so no F1 tricks will work here. I do think that a nose cone with a gap could still be more effective than not but it's not nearly as effective as a properly shaped wing/sail/airfoil.

And from our side, no about the credit card rule -- only applies to frame members in front of wheels (i.e. ST). Look at Look/Felt/Trek -- same thing with their fork/stems.

MC

--
Mark Cote
MITAerobike
Specialized Bicycle Components
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Re: Kestrel Wind tunnel data [MITaerobike] [ In reply to ]
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What if there is no gap? On my front water bottle design, the carbon extends all the way to the head tube, but is flexible to allow normal steerage to occur. Also, the bladder is setup to bulge out the sides to 1.1x the width of the HT at 1/3 of the overall length of water bottle + head/downtube interface. Unfortunately on a Softride, the trailing edge of that section is not that well designed.

Link here

Chris
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Re: Kestrel Wind tunnel data [chicanery] [ In reply to ]
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That looks gooooood...nice work! Yeah, that should work and will definitely help in a big way. Will it buldge out more than this when full? It looks like a pretty gentle shape so I'd expect airflow attachment on the downwind side up to and maybe past 10 degrees (just an estimate). If it buldges out any more, you'll probably be better in crosswind but a bit worse head on. Looks like a beautiful execution though. I would expect an execution like this to save 50ish grams of drag over a bare bike) at 30 mph from +/- 10 degrees, maybe more.

Hope I get to see it in person! Are you an engineer or just a very very good tinkerer?

Good luck with the TT and Tri-ing,

Mark

--
Mark Cote
MITAerobike
Specialized Bicycle Components
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Re: Kestrel Wind tunnel data [MITaerobike] [ In reply to ]
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Thank you for the kind words, Mark - really means a lot coming from ShivMan (I really do think you should go by that from now on - maybe even get a nice lycra TT suit with the Specialized logo and some other cool effects). The bulge is "tunable" as the sides are only a single layer thick at the 1/3 point and I have a couple of "skeleton" pieces that hold the bulge in the correct position when the bladder starts getting empty. There are a few different setups I can run depending on weather and length of the course...anywhere from 24oz to 48oz. I have a Kestrel 4500 weather meter that I use on course with some custom Google maps based software I've built to calculate average yaw on course. It's also legal for USAT events according to all of the rules I have been able to find - but only barely.

I am actually a software engineer, but my family is in cabinetry/carpentry and auto mechanics so I've been building random stuff for as long as I can remember. I really appreciate your input here.

Chris
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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Dangit, now I'm a hijacker too...


With 150-180g of tare drag "left off" I don't see any reason to doubt the Shiv #'s are real. I'm just wondering if the Shiv's lead would still seem massive when you add that drag back in...which I think you'd have to do if massiveness is judged in the context of data like Cervelo's. I point to their oft-posted/quoted drag comparison charts in this example because for the P3C and TTX, tested at the same facility (LSWT in this case), we and Cervelo get similar #s @0deg and at least stay in the same ballpark as yaw increases. We don't subtract out tare drag (never mind 150-180g worth) to arrive at our comparison #s...so I'm guessing it's still there in theirs too.


Let's play the game and say it's not...and let's also say LSWT's tare drag is probably in the same ballpark as A2's. Could you come up with 150-180g more drag via setups, sure...but given what you know - or suspect - about how folks like Cervelo do their testing, do you really think they're going to set their own bikes up in a manner that's 150-180g worse than it really has to be?




Carl

Carl Matson
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Re: Kestrel Wind tunnel data [chicanery] [ In reply to ]
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122 posts and counting on a thread that is nothing but speculation until the actual paper comes out. Perhaps I'll ask steve about it today. A chart is just a chart.... until you know how the chart was arrived we are all just spouting hot air.

________________________
34 kona qualifiers 2006-'19 - 3 Kona Podiums - 4 OA IM AG wins - 5 IM AG wins - 18 70.3 AG wins
I ka nana no a 'ike -- by observing, one learns | Kulia i ka nu'u -- strive for excellence
Garmin Glycogen Use App | Garmin Fat Use App
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Re: Kestrel Wind tunnel data [jmhtx] [ In reply to ]
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So Trek and Specialized has chimed in.

If Gerard would comment, I'm certain he would say he was glad to finish second in yet another manufacturer's wind tunnel data.

No comment from Kestrel, yet. I know there a little event in Kona, but....

Suffer Well.
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Re: Kestrel Wind tunnel data [MarkyV] [ In reply to ]
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Right. I see no reason why Steven can't just pop on here and dispel the assumptions and rumors we've made. Perhaps he's busy in the tunnel at A2 right now, or trying to get the 4000 under some pros in Kona, but a quick note would let us all sleep a little easier tonight.

Chris
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Re: Kestrel Wind tunnel data [chicanery] [ In reply to ]
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He's here in kona. It is entirely possible that he's been simply too slammed while out here and hasn't yet had the time to respond.

Heading that way now. If I see him I'll ask

________________________
34 kona qualifiers 2006-'19 - 3 Kona Podiums - 4 OA IM AG wins - 5 IM AG wins - 18 70.3 AG wins
I ka nana no a 'ike -- by observing, one learns | Kulia i ka nu'u -- strive for excellence
Garmin Glycogen Use App | Garmin Fat Use App
Quote Reply
Re: Kestrel Wind tunnel data [Carl] [ In reply to ]
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In Reply To:
We don't subtract out tare drag...to arrive at our comparison #s

Why not? That is, what is the logic behind this decision?
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Re: Kestrel Wind tunnel data [chicanery] [ In reply to ]
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dont be silly

he just posted in another thread a few minutes ago about the kestrel pro msrp or something like that. He as plenty of time to post as it s part of the job to be on slowtwitch if you are smart marketing wise.

He seems like a smart guy and milking this thread to the max and letting it go up in view and post before chipping in.... smart marketing. He will chip in when the thread start to die...


,

Jonathan Caron

Jonnyo Coaching
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Re: Kestrel Wind tunnel data [MarkyV] [ In reply to ]
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In Reply To:
He's here in kona. It is entirely possible that he's been simply too slammed while out here and hasn't yet had the time to respond.

Heading that way now. If I see him I'll ask

That's what Steve said in another thread -

Re: Kestral airfoil pro SE [sharad]
In Reply To:
Wind tunnel thread is interesting. I'm a bit slammed in Kona right now so give me until next week and I will chime in. Suffice it to say, the results are legit and tested in multiple ways against many of the bikes.

Off to the last day of the Ironman Expo.

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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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"I mean if the P4 is faster then the 4000 by a few seconds but I really dig the 4000 doesn't that count? "

I said if and the point of the post was to take into account someone's love for thier bike. I didn't say the 4000 and P4 where equals.

customerjon @gmail.com is where information happens.
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Re: Kestrel Wind tunnel data [Carl] [ In reply to ]
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In Reply To:
Dangit, now I'm a hijacker too...


With 150-180g of tare drag "left off" I don't see any reason to doubt the Shiv #'s are real ... Let's play the game and say it's not...and .. 150-180g more drag via setups


OK, so if I'm tracking with you correctly, this P3C below I tested at 689g at 0deg yaw in 2006 at LSWT

Below that is the Cervelo test, backs my numbers up, as does the test by Andy at TAMU (on a P3T)

so, subtract 150 to 180g for the tare ... you get to 500-530g

right in step with the Shiv's numbers from A2

so...

TTX 680g
P3C 680g
Shiv 650g (corrected for +150g tare)
P4 575g




Last edited by: gtingley: Oct 9, 09 14:25
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
In Reply To:
We don't subtract out tare drag...to arrive at our comparison #s

Why not? That is, what is the logic behind this decision?

Why? It's a constant unless you believe there's interaction between the bike and the struts that varies by bike as well as by yaw...or does this belong in a different basket than the rider-bike interaction you keep pointing out doesn't exist except in extreme cases?


So my question stands: does everyone else seem massively off the back once you put the tare drag back in?


Carl

Carl Matson
Last edited by: Carl: Oct 9, 09 14:40
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Re: Kestrel Wind tunnel data [gtingley] [ In reply to ]
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How much time over a 40k does -105g gain you? For real, I swear I am not being an ass.

customerjon @gmail.com is where information happens.
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Re: Kestrel Wind tunnel data [gtingley] [ In reply to ]
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Yes, that's exactly the road I'm trying to take you down. Though I might quibble with your inclusion of the P4...since it doesn't appear on the Cervelo chart you showed.


Carl

Carl Matson
Last edited by: Carl: Oct 9, 09 14:38
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Re: Kestrel Wind tunnel data [Carl] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
We don't subtract out tare drag...to arrive at our comparison #s

Why not? That is, what is the logic behind this decision?

Why? It's a constant unless you believe there's interaction between the bike and the struts that varies by bike as well as by yaw

No, that wasn't what I was attempting to imply...I just wondered why you wouldn't correct the data since you obviously have gone to the trouble of measuring the "wind on" tare.

In Reply To:
So my question stands: does everyone else seem massively off the back once you put the tare drag back in?

Obviously not, but here is why I am confused: I've always understood that they do correct for the tare at TAMU*, and since my wife's bike and Gary's bike appeared to have similar drags, assumed that the same was true at the LSWT. That is why I am/was so impressed by the numbers that Mark keeps quoting for the Shiv.

*I know for a fact that they do when presenting bike+rider data.
Last edited by: Andrew Coggan: Oct 9, 09 15:01
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Re: Kestrel Wind tunnel data [Carl] [ In reply to ]
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In Reply To:
Yes, that's exactly the road I'm trying to take you down. Though I might quibble with your inclusion of the P4...since it doesn't appear on the Cervelo chart you showed.


Carl

got it ... I added the links to each test on the title of the model, if you roll over the model titles in my post above, you can click the links

here is the P4 test http://www.mpstraining.com/firm-news/drag2.jpg
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Re: Kestrel Wind tunnel data [Mr. Tibbs] [ In reply to ]
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In Reply To:
How much time over a 40k does -105g gain you? For real, I swear I am not being an ass.

The aero rule of thumb is 50g = 0.5sec/km at 30mph
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
In Reply To:
We don't subtract out tare drag...to arrive at our comparison #s

Why not? That is, what is the logic behind this decision?

Why? It's a constant unless you believe there's interaction between the bike and the struts that varies by bike as well as by yaw

No, that wasn't what I was attempting to imply...I just wondered why you wouldn't correct the data since you obviously have gone to the trouble of measuring the "wind on" tare. Nothing to correct. Nothing measured either, for that matter. The only reason to measure it is to do something like Specialized did and wow everyone with #s that, upon thoughtful examination, maybe aren't all that special. At least they were up front about what they did, and now Mark has cued us in on the magnitude of what they did, and for that we should all be grateful.

In Reply To:
So my question stands: does everyone else seem massively off the back once you put the tare drag back in?

Obviously not, but here is why I am confused: I've always understood that they do correct for the tare at TAMU, and since my wife's bike and Gary's bike appeared to have similar drags, assumed that the same was true at the LSWT. That is why I am/was so impressed by the numbers that Mark keeps quoting for the Shiv.

details details... ;-)


Carl

Carl Matson
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Re: Kestrel Wind tunnel data [jmhtx] [ In reply to ]
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In Reply To:

Ignore the number differences for the moment and look at the shapes.

Cervelo says that the P3 is best at 10° and going an extra 5° adds about 50g onto the drag. According to Kestrel, the P3 bottoms out at 15°, which is about 50g better than at 10°.

PS. I work on the principal of not trusting people who use curves instead of straight lines to join the dots!
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Re: Kestrel Wind tunnel data [gtingley] [ In reply to ]
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Thanks...but I'm still not quite on board with the P4 data. The charts you link to for the P3C and the P4 seem to be based on the same datasets, the legend on the latter chart showing the same LSWT run codes (#s in front of the bike names) as on the former but the data have been rotated about 0deg yaw by a factor that is congruent with a cos beta squared correction. Could be something else I suppose. Anyway, not necessarily a big deal by itself, but that same familiarity with LSWT's date code convention (the 4digit code in the title of the chart containing the TTX, and the 4digit code after the P4 in the other chart's legend) also tells me the P4 data was likely generated some 7-8mo after everything else on the chart and dropped in there without any indication to that effect other than 4 extra numbers in the legend that few people will recognize or understand the potential significance of.


Maybe Cervelo has done something similar to Specialized's 6mo control study (cool stuff BTW), wouldn't surprise me, but I've seen no mention of it. Maybe there's another explanation altogether. In the meantime I, for one, don't take the chart with the P4 at face value.


Carl

Carl Matson
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Re: Kestrel Wind tunnel data [gtingley] [ In reply to ]
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But isn't the elephant in the room the Kestrel 4000 at around 500 g-f tared out?

I have to say though as time passes, I'm less and less interested in Kestrel's explanation of that chart (curvy or not).

To Carl: heck where's that Speed Concept data and the 2010 rollout? ;-)
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Re: Kestrel Wind tunnel data [rmur] [ In reply to ]
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In Reply To:
But isn't the elephant in the room the Kestrel 4000 at around 500 g-f tared out?

Who says that the struts aren't tared out already? See...that's the problem...insufficient details.

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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In Reply To:
In Reply To:
But isn't the elephant in the room the Kestrel 4000 at around 500 g-f tared out?

Who says that the struts aren't tared out already? See...that's the problem...insufficient details.

DA 725g http://i33.tinypic.com/25jjszm.jpg
TTX 680g http://i33.tinypic.com/25jjszm.jpg
P3C 680g http://i33.tinypic.com/25jjszm.jpg
4000 675g (corrected for +150g tare) http://www.xtri.com/...p/img_rep_5981_1.jpg
Shiv 650g (corrected for +150g tare) http://forum.slowtwitch.com/...post=2536314#2536314
P4 575g http://www.mpstraining.com/firm-news/drag2.jpg
Quote Reply
Re: Kestrel Wind tunnel data [gtingley] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
But isn't the elephant in the room the Kestrel 4000 at around 500 g-f tared out?

Who says that the struts aren't tared out already? See...that's the problem...insufficient details.

DA 725g http://i33.tinypic.com/25jjszm.jpg
TTX 680g http://i33.tinypic.com/25jjszm.jpg
P3C 680g http://i33.tinypic.com/25jjszm.jpg
4000 675g (corrected for +150g tare) http://www.xtri.com/...p/img_rep_5981_1.jpg
Shiv 650g (corrected for +150g tare) http://forum.slowtwitch.com/...post=2536314#2536314
P4 575g http://www.mpstraining.com/firm-news/drag2.jpg

How do you account for the following data then in the grand scheme of things (i.e. where the p3C and Transition are fairly close, yet the Shiv is much better than the Transition?)





http://bikeblather.blogspot.com/
Quote Reply
Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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Those two graphs show the tare difference quite nicely I must add. And I don't know if this accounts for the difference, but didn't specialize test w/ the old wolf cl (or was it a tt) fork and not the 3t funda fork that Gerard claims is a significant improvement. I for one would be interested in knowing how much an improvement the new "cervelo" fork is over the 3t on the P3. (Further thread jacking this thread)

p.s. any engineer that uses curvy lines to connect data points should turn their sheepskin back in. That is strictly a marketing dept. thing and should remain so.
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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But isn't the elephant in the room the Kestrel 4000 at around 500 g-f tared out?

Who says that the struts aren't tared out already? See...that's the problem...insufficient details.

DA 725g http://i33.tinypic.com/25jjszm.jpg
TTX 680g http://i33.tinypic.com/25jjszm.jpg
P3C 680g http://i33.tinypic.com/25jjszm.jpg
4000 675g (corrected for +150g tare) http://www.xtri.com/...p/img_rep_5981_1.jpg
Shiv 650g (corrected for +150g tare) http://forum.slowtwitch.com/...post=2536314#2536314
P4 575g http://www.mpstraining.com/firm-news/drag2.jpg

How do you account for the following data then in the grand scheme of things (i.e. where the p3C and Transition are fairly close, yet the Shiv is much better than the Transition?)



I don't think the L is really a truly comparable bike to a 56. There's a lot less bike on a L than a 56. I brought that up with Mark in a previous thread. Not sure how that factors in, but it's something to consider. I think the XL and 56 are much more comparable. I.e., that's the size I'd ride in each. The L would be much too small (need like a 13cm stem on the L vs. a 10cm stem on the 56 P3C to achieve the same position).

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Kestrel Wind tunnel data [Rappstar] [ In reply to ]
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I don't think the L is really a truly comparable bike to a 56. There's a lot less bike on a L than a 56. I brought that up with Mark in a previous thread. Not sure how that factors in, but it's something to consider. I think the XL and 56 are much more comparable. I.e., that's the size I'd ride in each. The L would be much too small (need like a 13cm stem on the L vs. a 10cm stem on the 56 P3C to achieve the same position).

Reach-wise, yes, but not stack-wise. The L Transition actually has ~1cm greater stack than the 56 P3C (which accounts for ~0.3cm of the shorter reach.)

Besides, the XL was changed for 2010 and now has a 2cm higher stack, as opposed to the previous years where the stacks on the L and XL sizes only differed by 1mm.

I also find it sort of interesting that you'd ride those 2 sizes...since, IIRC, I'm at least 3" shorter than you, and a 56 P3C is what I had borrowed for the "Something Borrowed..." testing (and fit great) and I'm thinking about getting a L Transition. Of course, the fact that I'm now running a Scott 100K bar probably has some influence on that (i.e. it requires a shorter stem for a given pad position than the Vision bars I had used on the P3C).

In any case, you lost the point I was trying to make, which wasn't how the P3C compared to the Transition, but how the P3C compared (by inference) to the Shiv...and how that didn't match Gary's summary above.

http://bikeblather.blogspot.com/
Last edited by: Tom A.: Oct 9, 09 21:24
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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But isn't the elephant in the room the Kestrel 4000 at around 500 g-f tared out?

Who says that the struts aren't tared out already? See...that's the problem...insufficient details.


I was looking at the P3C to 4000 differential on the Kestrel chart ~175 g-f. If the P3C 'true' baseline is ~675 g-f that puts the K4000 down around 500 g-f. If the P3C/Fuji data isn't tared out, surely they wouldn't tare out the 4000?? (!!!!)

Re the Shiv/Transition differential - just ran some averages and across (-5,0,+5) it's -82g-f for the Shiv; across (-15,-10,+10,+15) it's -190g-f. Makes Zirbel's ride at the Worlds look all the more impressive eh?

Has anyone seen any Giant Trinity Advanced (nosecone) data BTW???
Last edited by: rmur: Oct 10, 09 5:34
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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I actually think you missed the point *I* was trying to make. It seems that it is somewhat arbitrary what size bike is chosen for these tests. Or rather it seems only stack height is considered, which is maybe not the best way. Maybe it is. But that would sem to ignore the length of the bike, which has to make SOME difference.

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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It would indeed be a mistake for Steven not to show up and lay out the protocol now that the data has been "released", with specifics on equipment used for all 4 frames.

<sound of crickets chirping>
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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It would indeed be a mistake for Steven not to show up and lay out the protocol now that the data has been "released", with specifics on equipment used for all 4 frames.

<sound of crickets chirping>

until then ...

DA 725g http://i33.tinypic.com/25jjszm.jpg
TTX 680g http://i33.tinypic.com/25jjszm.jpg
P3C 680g http://i33.tinypic.com/25jjszm.jpg
4000 675g (corrected for +150g tare) http://www.xtri.com/...p/img_rep_5981_1.jpg
Shiv 650g (corrected for +150g tare) http://forum.slowtwitch.com/...post=2536314#2536314
P4 575g http://www.mpstraining.com/firm-news/drag2.jpg
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Re: Kestrel Wind tunnel data [Mr. Tibbs] [ In reply to ]
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Since the old KM40 (the one with the curved down tube and 650 wheels) has been out of production for several years now, and since I own one, I often wonder how it would stack up aerodynamic with the newer bikes like the P3 and Specialized Transition. It seems like if it was properly outfitted with vision tech handlebars, disk wheel, and tri spoke front wheel, it would have to be pretty close, but I'm just an uninformed enthusiast grasping straws perhaps.

Geoff from Indy
http://www.tlcendurance.com
http://geoffreydean.wordpress.com/
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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It would indeed be a mistake for Steven not to show up and lay out the protocol now that the data has been "released", with specifics on equipment used for all 4 frames.

<sound of crickets chirping>

<chirp....chirp...chirp>

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [gtingley] [ In reply to ]
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Dangit, now I'm a hijacker too...


With 150-180g of tare drag "left off" I don't see any reason to doubt the Shiv #'s are real ... Let's play the game and say it's not...and .. 150-180g more drag via setups


OK, so if I'm tracking with you correctly, this P3C below I tested at 689g at 0deg yaw in 2006 at LSWT

Below that is the Cervelo test, backs my numbers up, as does the test by Andy at TAMU (on a P3T)

so, subtract 150 to 180g for the tare ... you get to 500-530g

right in step with the Shiv's numbers from A2

so...

TTX 680g
P3C 680g
Shiv 650g (corrected for +150g tare)
P4 575g

Hey hey hey, slow down ---- Let's be scientific. The tare values at A2 and San Diego ARE NOT THE SAME! The tunnels are not the same. The data can not be compared like that. We took our control bike to 5 different tunnels last year and while 0 degrees generally lines up, yaw does not. We've talked about this on ST before. And I have to read lower in this thread too, but just got to this post and had to raise a red flag.

Mark

--
Mark Cote
MITAerobike
Specialized Bicycle Components
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Re: Kestrel Wind tunnel data [Carl] [ In reply to ]
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We don't subtract out tare drag...to arrive at our comparison #s

Why not? That is, what is the logic behind this decision?

Why? It's a constant unless you believe there's interaction between the bike and the struts that varies by bike as well as by yaw

No, that wasn't what I was attempting to imply...I just wondered why you wouldn't correct the data since you obviously have gone to the trouble of measuring the "wind on" tare. Nothing to correct. Nothing measured either, for that matter. The only reason to measure it is to do something like Specialized did and wow everyone with #s that, upon thoughtful examination, maybe aren't all that special. At least they were up front about what they did, and now Mark has cued us in on the magnitude of what they did, and for that we should all be grateful.
MIT Aerobike Response --- Nope, I subtract tares so that the raw corrected values are representative of real world drag values that can be used when comparing to power testing. I don't have an apparatus mounted to my bike when I do power testing, so I don't include that drag. If there is assumed very little apparatus interaction with the bike, then the tare should be subtracted. At MIT, it wasn't a good idea to subtract because there was a fair amount of apparatus interaction with the bike. At A2, there isn't, so I subtract tares. We publish in grams of force because people like seeing that. I study in CdA (m^2) and want all of my wind tunnel data to be useable for real world simulations.
In Reply To:

--
Mark Cote
MITAerobike
Specialized Bicycle Components
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Re: Kestrel Wind tunnel data [MITaerobike] [ In reply to ]
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--- Nope, I subtract tares so that the raw corrected values are representative of real world drag values that can be used when comparing to power testing. I don't have an apparatus mounted to my bike when I do power testing, so I don't include that drag.

Yeah...I was thinking the same thing when Carl made that comment...why wouldn't you want to subtract the tare. That would make it slightly easier to compare across tunnels too, right?


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We publish in grams of force because people like seeing that.

I think it's time to start changing that paradigm and publish in CdA (m^2) as the primary "units" ...and just give "grams @ 30mph, STP, etc." as a reference :-)


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I study in CdA (m^2) and want all of my wind tunnel data to be useable for real world simulations.

Amen...but, does that mean you've convinced the A2 folks to report CdA in m^2 instead of ft^2 ;-)

http://bikeblather.blogspot.com/
Last edited by: Tom A.: Oct 14, 09 15:49
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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Still no Steven, huh? That's a shame.
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Re: Kestrel Wind tunnel data [hgrong] [ In reply to ]
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Still no Steven, huh? That's a shame.

As I wrote earlier today:

<chirp....chirp...chirp...>

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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All,

Sorry for the chirp chirp as you like to say...

So, let me explain how Kestrel does our testing and why I feel that a complete bike test benefits the consumer.

First, all my design and testing is done @ the A2 Tunnel. I feel that it is the one of greatest assests I have that there is a tunnel with expertise available.

Testing was done on all bikes with Zipp Disc ad Zipp 404 and also tested with Zipp 404 and 808's.

The goal was to see how each wheel affected the bike. We also tested multiple bars on each bike along with specific components. Again, how do parts change the data on the complete bike.

I tested the same size bikes, same saddle height, same bar height.

Bars tested were what I spec on bikes. 3T Mistral Pro, Zipp Vuka, and Profile Cobra Wing with T-1 Viper Extensions. Each bike was tested with the same bars since I know that this would affect the test.

I left the drive train components alone meaning that if Brand X used Shimano Dura Ace and I spec'd Sram Red, it would remain the same.

I also used 23mm tires on all bikes.

The one issue is that you can NOT compare data from one tunnel test to another @ the same tunnel or from tunnel to tunnel. So what you see from a competitor's test will show differently.

Hope that answers some questions.
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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All,

Sorry for the chirp chirp as you like to say...

No problem...you're a busy guy after all ;-)


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So, let me explain how Kestrel does our testing and why I feel that a complete bike test benefits the consumer.

First, all my design and testing is done @ the A2 Tunnel. I feel that it is the one of greatest assests I have that there is a tunnel with expertise available.


Mark Cote speaks highly of them as well...


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Testing was done on all bikes with Zipp Disc ad Zipp 404 and also tested with Zipp 404 and 808's.


So...what wheels were on the particular bikes in the plot shown in the first post in this threas?



In Reply To:
The goal was to see how each wheel affected the bike. We also tested multiple bars on each bike along with specific components. Again, how do parts change the data on the complete bike.

I tested the same size bikes, same saddle height, same bar height.


Do you mind if I ask how the saddle heights and bar heights were measured?




In Reply To:
Bars tested were what I spec on bikes. 3T Mistral Pro, Zipp Vuka, and Profile Cobra Wing with T-1 Viper Extensions. Each bike was tested with the same bars since I know that this would affect the test.

Does that mean that each bike in the test (including the competitors) was tested with each bar? If so, again, what configuration does the plot represent?



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I left the drive train components alone meaning that if Brand X used Shimano Dura Ace and I spec'd Sram Red, it would remain the same.

I also used 23mm tires on all bikes.


Fair enough.



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The one issue is that you can NOT compare data from one tunnel test to another @ the same tunnel or from tunnel to tunnel. So what you see from a competitor's test will show differently.


Are you saying that the repeatability of the A2 tunnel in respect to CdA measurements isn't very good? Or...are you commenting on the drag values in grams?



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Hope that answers some questions.

It's a start ;-)

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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Steve-
Could you just list the parts that were used on the 4 bikes to get the 4 lines on your graph?

i.e.
P3C-
bars -brand x
front wheel - brand z model a
rear wheel - brand z model b
....
4000-
bars -brand h
front wheel - brand z model c
rear wheel - brand z model d
....
also the big tunnel next door has very little problem repeating test session to test session, why would the small tunnel be any different?
bars
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Re: Kestrel Wind tunnel data [MITaerobike] [ In reply to ]
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We took our control bike to 5 different tunnels last year and while 0 degrees generally lines up, yaw does not. We've talked about this on ST before.

Hmmm. I missed that thread, and it is pertinent to something I'd wondered about for a while. Can you point to that discussion?
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Re: Kestrel Wind tunnel data [RChung] [ In reply to ]
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I have to say i do appreciate the fact that some engineer like Mark Cote and Gerard take part in our discussion because the level of precision and explanation they give to explain there testing is just on a differente level. Make things a lot more clear and transperante to me.

Jonathan Caron

Jonnyo Coaching
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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As others have said; thanks for replying! Just the two questions from me:

What speed was the test run at?

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The one issue is that you can NOT compare data from one tunnel test to another @ the same tunnel or from tunnel to tunnel. So what you see from a competitor's test will show differently.

I can understand that the values might not be the same, but surely the shape of the curves should be largely similar if not the same?

Regarding your point about results which shouldn't be directly compared; people might be interested to know that it's been revealed recently that is how the aero data on the HED site was obtained (apparently using different protocol too).
Last edited by: zebragonzo: Oct 15, 09 9:40
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Re: Kestrel Wind tunnel data [RChung] [ In reply to ]
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We took our control bike to 5 different tunnels last year and while 0 degrees generally lines up, yaw does not. We've talked about this on ST before.

Hmmm. I missed that thread, and it is pertinent to something I'd wondered about for a while. Can you point to that discussion?

Hmmm...I found these 2 posts merely by searching on "control" and author "MITAerobike" ;-)

http://forum.slowtwitch.com/...ing=control;#2014644

http://forum.slowtwitch.com/...ing=control;#2394452

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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There are three big research projects we did in aero in parallel with Transition/Shiv development over the past two years:

1. Comparison on a control bike at several different wind tunnels (A2WT, UWAL, SD LSWT, MIT WBWT, AAT Fort Collins)

2. Long term testing repeatability of a control bike at the A2 Wind Tunnel

3. Comparison of Road versus Aero gear for TT/Tri racing (wind tunnel and power testing study)

The first two were internal studies, the third I've posted up here before. I'll continue to share parts of the internal studies as appropriate.

Cheers,

Mark

--
Mark Cote
MITAerobike
Specialized Bicycle Components
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Re: Kestrel Wind tunnel data [MITaerobike] [ In reply to ]
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In Reply To:
There are three big research projects we did in aero in parallel with Transition/Shiv development over the past two years:

1. Comparison on a control bike at several different wind tunnels (A2WT, UWAL, SD LSWT, MIT WBWT, AAT Fort Collins)

2. Long term testing repeatability of a control bike at the A2 Wind Tunnel

3. Comparison of Road versus Aero gear for TT/Tri racing (wind tunnel and power testing study)

The first two were internal studies, the third I've posted up here before. I'll continue to share parts of the internal studies as appropriate.

Cheers,

Mark

Damn...you've got a fun job...I'm jealous :-)

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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"Damn...you've got a fun job...I'm jealous :-)"

x2. Beats the hell out of designing and testing the watertightness and/or EMI radiation characteristics of, say, a modified Gichner S280 military shelter.
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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Zipp Disc and 404 were used on the chart shown.

Saddle height I'll have to check although each bike was the same as were the bars.

Each bike was tested with each bar. The test shows the Zipp Vuka bar.

What I am saying is that every time you go into a tunnel it is an individual test. You can't compare one tunnel test to another test. Has nothing to do with the tunnel quality.
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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Speed?
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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so this thread keeps saying wind tunnel data....will there be a release of the actual paper at some point in the near future?

also, do you have geometries on the 4000?

________________________
34 kona qualifiers 2006-'19 - 3 Kona Podiums - 4 OA IM AG wins - 5 IM AG wins - 18 70.3 AG wins
I ka nana no a 'ike -- by observing, one learns | Kulia i ka nu'u -- strive for excellence
Garmin Glycogen Use App | Garmin Fat Use App
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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Something is just not right about this.

The BIG issue was if they used the same wheels and bars on all bikes for these tests. Kestrel is now saying they did. Why not release that information when the results were made public? Why wait two weeks during which time lots of negative stuff is written about your company? That and the fact that your competitors bikes are shown to produce over 100 grams more drag at 0 degrees then multiple independent tests.

Something just does not add up.
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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In Reply To:
Zipp Disc and 404 were used on the chart shown.

Saddle height I'll have to check although each bike was the same as were the bars.

Each bike was tested with each bar. The test shows the Zipp Vuka bar.
Then the chart is wrong in saying that "each bike was tested as supplied to the consumer"?
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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It appears that no amount of time responding to questions will be sufficient to those in this thread, so I am surprised Kestrel even spends any time addressing it.

---
Team Triabetes
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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It looks like Kestrel designed the most aero bike that they could, fair enough.
However, that transition between the seat post and the seat stays reminds me of a full-suspension mountain bike. I think a lot of energy will be wasted per pedal stroke by having that notch.

Am I on crack ? Is there a way to test power transfer between bikes - i.e. is this frame stiffer or as stiff as the others ?

I'm just wondering, I really NEED a new TT bike for next year :) .
Thanks - Mark
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Re: Kestrel Wind tunnel data [kemp] [ In reply to ]
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There will always be questions. But, the issue comes when something is published that basically says "look how great our new bike is...it's the fastest on the planet" and there is really nothing too concrete about how the testing was done, etc. Or, the small print says one thing like "bikes were tested as they would be delivered to the consumer" when maybe only one of the bikes would be delivered to the consumer with race wheels. You can punch holes in any study that gets published, and if you publish something that is less than complete or at least less than open with how things have been done, you can expect to have lots of questions...especially by folks who have done similar windtunnel or PM/outdoor testing like AC, MITaerobike, TomA, and others.


Brandon Marsh - Website | @BrandonMarshTX | RokaSports | 1stEndurance | ATC Bikeshop |
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Re: Kestrel Wind tunnel data [kemp] [ In reply to ]
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It appears that no amount of time responding to questions will be sufficient to those in this thread, so I am surprised Kestrel even spends any time addressing it.

So we should just accept the numbers even though by Kestrels own admission the chart is wrong?
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Re: Kestrel Wind tunnel data [kemp] [ In reply to ]
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IF they want to sell bikes in a packed field with a for crap economy...... I'd say it's in their BEST interest !
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Re: Kestrel Wind tunnel data [Zooma] [ In reply to ]
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The chart is not wrong and maybe I'm not explaining it well.

We tested in a fair way that we believe shows real #'s.

To you the consumers, we tested with the same wheels, bars, etc. We ALSO tested as the bikes come to you the consumer which is really all how I feel the industry should test complete bikes that the consumer rides. I choose parts based on what I know works both mechanically and in the tunnel. Note that my bar selection on the bikes at the high end is my most aero bar tested. Same with wheels.

Wind tunnel data can be picked apart and I'm happy to have the new Kestrel 4000 tested by independently.
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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In Reply To:
we tested with the same wheels, bars, etc. We ALSO tested as the bikes come to you the consumer
So which data are presented in the chart?
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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In Reply To:
Zipp Disc and 404 were used on the chart shown.

Saddle height I'll have to check although each bike was the same as were the bars.

I'm sorry...I probably wasn't clear. I meant to what reference were each measured? The ground?


In Reply To:
Each bike was tested with each bar. The test shows the Zipp Vuka bar.

What I am saying is that every time you go into a tunnel it is an individual test. You can't compare one tunnel test to another test. Has nothing to do with the tunnel quality.

I'm not so sure if the folks at A2 would totally agree with such an absolute statement. There HAS to be some measure of repeatability possible...otherwise, what's the point? Yeah, the tests won't be exactly the same, but they should be able to repeat the results to within +/- some value of CdA.

Is it possible you guys could post pics from the runs? Those always help explain things a LOT...

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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He answered that before. The chart in this thread is with Disc rear, and 404 front with Vuka aerobars.

Chris
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Re: Kestrel Wind tunnel data [chicanery] [ In reply to ]
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In Reply To:
He answered that before. The chart in this thread is with Disc rear, and 404 front with Vuka aerobars.

Chris
Steve said "the chart is not wrong", which could be interpreted to mean that he stands by the data presented, OR to mean that they are from bikes as delivered to the consumer.
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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In Reply To:
The chart is not wrong and maybe I'm not explaining it well.

We tested in a fair way that we believe shows real #'s.

To you the consumers, we tested with the same wheels, bars, etc. We ALSO tested as the bikes come to you the consumer which is really all how I feel the industry should test complete bikes that the consumer rides.

If you are saying that the chart shows drag numbers for bikes as they are delivered to consumers I may believe you.

If you are saying that the chart shows drag numbers with ALL bikes equipped with aero wheels then I say bullshit.

I think you said option 2 was the setup for the chart so I am saying I don't believe you.

Your company may have made an amazing bike but in my mind you have totally blown your credibility with the way you have presented the data. Why not come clean and just answer the questions put to you?
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Re: Kestrel Wind tunnel data [Zooma] [ In reply to ]
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nobody cares what you believe. They posted date, and then explained what it is and how they got it. Go back to riding your P3.

chris
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Re: Kestrel Wind tunnel data [chicanery] [ In reply to ]
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If I had wanted your input I would have asked for it. Fuck off!!!
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Re: Kestrel Wind tunnel data [Zooma] [ In reply to ]
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If I had wanted your input I would have asked for it. Fuck off!!!

I don't remember anyone in this thread asking for your opinion either, but that didn't stop you from spouting off.
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Re: Kestrel Wind tunnel data [hgrong] [ In reply to ]
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The difference is my questions and comments were directed to the OP. That's how this forum thing works. You or your buddy Christopher may not like my questions. No problem. I don't like marketing bullshit or people not answering direct questions on a topic they started.
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Re: Kestrel Wind tunnel data [jmhtx] [ In reply to ]
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In Reply To:

Could I just point out several things that make the data look slightly amateur:
1) Data analysis - I can see data, but where's the analysis (or is that a prelude to this thread?)
2) Scientists use straight lines, marketing people use curved lines; unless you know how the data varies between two points, assume it's linear.
3) Basic information is missing; the speed was the test conducted at is one such key bit of info.
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Re: Kestrel Wind tunnel data [zebragonzo] [ In reply to ]
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Amateur??

I would have to say that you should take that up with the A2 guys since this is what we receive from them.

Great debates none the less but I will tell you I stand by the data.

The A2 tunnel is one of the best and the data and chart were supplied and reviewed while I was @ the tunnel. Nothing has been changed from their report.
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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I tried asking politely ;-)

Just because it comes from the wind tunnel, it doesn't automatically make them right.

Also, what speed was the testing done at?
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Re: Kestrel Wind tunnel data [zebragonzo] [ In reply to ]
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If 'scientists' use straight lines for stuff like this, I'd suggest they're implying a level of linearity which simply isn't there. If there was anything to be learned from the Hed data taken at 2.5 degree sweeps, it's that the data isn't necessarily linear.

Granted we're talking about wheels vs. bikes, but I still wouldn't assume the data is linear between 5 degree points. I actually think the way it's presented here is more reasonable, regardless of 'what scientists may think'.

I would actually think that 'scientists' wouldn't connect the dots in the first place....
Last edited by: roady: Oct 18, 09 9:37
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Re: Kestrel Wind tunnel data [roady] [ In reply to ]
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In Reply To:
If 'scientists' use straight lines for stuff like this, I'd suggest they're implying a level of linearity which simply isn't there. If there was anything to be learned from the Hed data taken at 2.5 degree sweeps, it's that the data isn't necessarily linear.

You may be missing the point - you don't assume that the data is linear, you use linear data unless you can prove otherwise.

edit - remember that there is only one straight line that can be drawn between points, there are an infinite number of curves.
Last edited by: zebragonzo: Oct 18, 09 9:45
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Re: Kestrel Wind tunnel data [zebragonzo] [ In reply to ]
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I get the point, but as a non-scientist I actually think that the curved line presents an ambiguous interpretation which is probably more representative of reality--at least to this layman.
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Re: Kestrel Wind tunnel data [zebragonzo] [ In reply to ]
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yes but that doesn't mean the data doesn't show this. Just because they marked the major points 5,10,15 etc doesn't mean they didn't collect data through the whole range.

You can't mark a data point every .000000001 degrees thats what a line is for. You're assuming they only collected 5 points of data during the sweep which i doubt is true.
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Re: Kestrel Wind tunnel data [roady] [ In reply to ]
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In Reply To:
If 'scientists' use straight lines for stuff like this, I'd suggest they're implying a level of linearity which simply isn't there. If there was anything to be learned from the Hed data taken at 2.5 degree sweeps, it's that the data isn't necessarily linear.

Granted we're talking about wheels vs. bikes, but I still wouldn't assume the data is linear between 5 degree points. I actually think the way it's presented here is more reasonable, regardless of 'what scientists may think'.

I would actually think that 'scientists' wouldn't connect the dots in the first place....
Scientists would connect the dots, with straight lines, because it makes the data much easier to see than scatter plot, especially when it's small. It's hard to see which points are related.

The one other thing that scientists would do is include error bars at each data point, but that's probably asking too much.

The reason that you do not connect with a curved line is that is makes an implication of what is not there. I'm sure A2 does it because they are in the marketing business as well. There are now enough windtunnels that there is competition for bike testing business. The curved lines look "pretty," but they are incorrect.

If you connect the dots with straight lines, everyone knows it simply for visual clarity. If you connect it with a curved line, there can be the assumption that there actually is a fit that has been applied. Unfortunately, in this case, there was not. You don't know if the data goes from a-to-b like this / or like this _| or like _( or like ^ or... (sorry, I ran out of approximations using common characters). The data could move logarithmically or exponentially or parabolically, all which would mean very different things. And when you put an arbitrary curve in, that is, as zebragonzo said, "amateur."

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Kestrel Wind tunnel data [draketriathlon] [ In reply to ]
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In Reply To:
yes but that doesn't mean the data doesn't show this. Just because they marked the major points 5,10,15 etc doesn't mean they didn't collect data through the whole range.

You can't mark a data point every .000000001 degrees thats what a line is for. You're assuming they only collected 5 points of data during the sweep which i doubt is true.
No, it is true. That's how you measure. In ~2.5deg increments. Every time you rotate the balance, you have to then wait for the reading to stabilize. You don't take measurements while the balance is in motion.

They do collect more than five (or ten) points, but it's multiple sets of data at those same five (or ten) points and you also hit those points twice per run (if you are testing correctly) - on the sweep out and then the sweep back in. I.e., you have Run_One[0, 2.5, 5, 7.5, 10, 12.5, 15, 17.5, 20, 17.5, ... , 0], Run_Two[..], Run_Three, etc. Then you take an average value at each point, which is also what yields the error margin for each reading. You probably also kick out a bad run, if you have one set where the data is way outside the normal deviation.

They definitely don't measure every 0.00001 degrees.

The criticisms that everyone has made of the way the data has been presented are valid.

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Kestrel Wind tunnel data [Rappstar] [ In reply to ]
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Okay good to know.. makes sense.

I was more concerned with that we have no clue what bike was actually tested more then the curved data lines. I can deal with that.
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Re: Kestrel Wind tunnel data [Rappstar] [ In reply to ]
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In Reply To:
The reason that you do not connect with a curved line is that is makes an implication of what is not there. I'm sure A2 does it because they are in the marketing business as well.

IMO a more likely explanation is simply that whomever drew the plot just wasn't anal-retentive enough to change the default setting in Excel...
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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In Reply To:
Amateur??

I would have to say that you should take that up with the A2 guys since this is what we receive from them.

Great debates none the less but I will tell you I stand by the data.

The A2 tunnel is one of the best and the data and chart were supplied and reviewed while I was @ the tunnel. Nothing has been changed from their report.

Hmmm. You are missing the point zebragonzo made.

He didn't question the data behind what was presented. I don't think anyone really questions the data coming out of A2.
He (and others) questioned what was presented.
Who made the chart, Kestrel or A2?
The title says "ANALYSIS". Where is the analysis?
Where is the rest of the data that A2 no doubt provided?
What speed/condition/dynamic pressure was used or normalized to?
Others have asked specifically about frame of reference for heights and angles, wheels tested vs wheels delivered etc etc. Where are the answers?

Hmmm.
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Re: Kestrel Wind tunnel data [sharad] [ In reply to ]
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Is there a reason that you occasionally pop into this thread, defend your graphs with little to no data, then run away? Is it that difficult? Frankly, you're demeanor on this thread makes yourself and the rest of your company look like a bunch of idiots that think they can throw a pretty graph up and convince everyone.

You obviously paid a lot of money developing the bike, and a lot more testing. What's the difficulty in paying another several man hours to write up and release a decent white paper, and release photos? If your protocol was in fact as sound as you claim, then doing so will only help your cause.

Personally, I like the fit of this bike. I also like the fit of several other, similar bikes, which have been proven openly in the tunnel. I'm also looking for a fast bike for '10. As I stand right now, I love this bike, and will buy it in a heartbeat, if it can be shown to me that it's actually better than, or at least comparable to, the other bikes that fit similarly. With the data currently presented however, my view is that you have a sub-optimal bike, are fudging data to present otherwise, and as a result, I have zero interest in purchasing said bike. From that angle, the profit you would make off of me would cover the cost in man-hours for doing the writeup. Add in everyone else here, and the fact that many of us are considered at least local experts in aerodynamics, seems like an easy call.
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Re: Kestrel Wind tunnel data [Andrew V] [ In reply to ]
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+1
But then again, he only replies to Coggan and Tom A.

I think Steve should start a new thread to present the data in full - in his own words - and allow the "experts" their opinions, which excludes me.

Like he'll read this message.... anyway,......... :)
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Re: Kestrel Wind tunnel data [jmhtx] [ In reply to ]
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Man, once again I am not feeling the love in this post, it is funny how some of these posts really sink downhill in a hurry with some people's attitudes. I guess that Kestrel should have sent this over to joshatzipp or Gerald to post it so you guys would believe it without questioning it.
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Re: Kestrel Wind tunnel data [gralden] [ In reply to ]
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In Reply To:
Man, once again I am not feeling the love in this post, it is funny how some of these posts really sink downhill in a hurry with some people's attitudes. I guess that Kestrel should have sent this over to joshatzipp or Gerald to post it so you guys would believe it without questioning it.

Do you really think that they don't get peppered with questions too?

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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No Tom, I know that you guys give them the business too .. :o). This post just seems to be getting a bit rough as it goes on. I am sure Kestrel will supply more data, some of the folks just need to chill out a little bit, maybe training more would help relieve some of the stress.....
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Re: Kestrel Wind tunnel data [gralden] [ In reply to ]
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In Reply To:
No Tom, I know that you guys give them the business too .. :o). This post just seems to be getting a bit rough as it goes on. I am sure Kestrel will supply more data, some of the folks just need to chill out a little bit, maybe training more would help relieve some of the stress.....

Good...I was worried we were slipping... ;-)

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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I never worry about you slipping Tom, I actually enjoy your thoughts and comments, I now there is a ton that I can and have already learned here on ST. I know that you are one of the true 'local experts' that we have on here and that is what is needed. I am always just a little concerned when others say they are 'experts' but do not have the experience here on ST to back it up.

Not to hijack this thread, but what are your thoughts on the new Easton 90mm TT wheel shown at Interbike, I did not see any comments from you on this thread, but I know you must be thinking something .... ;o)

http://forum.slowtwitch.com/...earch_engine#2516790
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Re: Kestrel Wind tunnel data [gralden] [ In reply to ]
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In Reply To:
No Tom, I know that you guys give them the business too .. :o). This post just seems to be getting a bit rough as it goes on. I am sure Kestrel will supply more data, some of the folks just need to chill out a little bit, maybe training more would help relieve some of the stress.....

It's getting rough because there are good questions being asked with no answers arriving. This is Kestrel's fault. They are having their new premier aero frame being slammed due to some guy being too busy to answer questions.

Ken

Ps. I know that no one is actually slamming the frame but the company in my opinion looks quite Mickey Mouse right now, due to no defense of their data.


"the trick is to keep losing weight until your friends and family ask you if you've been sick. then you know you're within 10 pounds. if they start whispering to each other, wondering if you've got cancer or aids, you're within 5. when they actually do an intervention, you're at race weight." - Slowman
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Re: Kestrel Wind tunnel data [gralden] [ In reply to ]
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I have no douth that the new kestrel will be a excellent bike. I have big douth that it is as good as the graph is showing but i m sure it will be a good bike none the less.

Would just be nice to have more specific answer and details. I think that any company that make a commitement to triathlon as to commit one of there engineer to come here to present and explain the results. This site as too much influence in the tri market in north america to leave all those question unanswered. Cervelo, trek, felt, scott were at the top of the list at ironman hawaii bike count....and they competant and knowledgable people that come here every now and then to answer (accuratly and precisely) the questions..... i kind a see a partner in this....

As for the Easton 90mm TT. I played with it at interbike. The hubs were amazing...very small and smooth....as smooth as zipp. The wheel overall seems very nicely made but tubular only. I wonder if it really test as good as the graph show but i m very curious about it none the less...

Jonathan Caron

Jonnyo Coaching
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Re: Kestrel Wind tunnel data [gralden] [ In reply to ]
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In Reply To:
No Tom, I know that you guys give them the business too .. :o). This post just seems to be getting a bit rough as it goes on. I am sure Kestrel will supply more data, some of the folks just need to chill out a little bit, maybe training more would help relieve some of the stress.....
I think it got rough for two reasons.

1) there was a lot of talk beforehand about when the data would be released, how novel the testing concept was, etc. I.e., there was quite a bit of hype before anything was actually shown. Some bold claims were made about performance relative to very good bikes. So there was pretty big talk from Kestrel beforehand.

2) there was a LONG period of total silence from Kestrel with regards to the claims made above.

3) when the data was finally presented, it was very ambigious

4) even after the data was presented, explanations and clarifications of the data haven't been exactly forthcoming.

I don't think it's the data itself as much as what Andrew V alluded to - lack of communication, information, etc. that is reflecting poorly, IMO, upon Kestrel. Andrew V hit the nail on the head - they spent money on development, testing, etc. but couldn't hire someone to write up a 10 page white paper?

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Kestrel Wind tunnel data [gralden] [ In reply to ]
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In Reply To:
I never worry about you slipping Tom, I actually enjoy your thoughts and comments, I now there is a ton that I can and have already learned here on ST. I know that you are one of the true 'local experts' that we have on here and that is what is needed. I am always just a little concerned when others say they are 'experts' but do not have the experience here on ST to back it up.

Not to hijack this thread, but what are your thoughts on the new Easton 90mm TT wheel shown at Interbike, I did not see any comments from you on this thread, but I know you must be thinking something .... ;o)

http://forum.slowtwitch.com/...earch_engine#2516790

I actually didn't look at those in Vegas...but, as others pointed out in the thread, how well it performs relative to similar wheels can be easily influenced by tire choice.

That said, narrow hubs and low spoke counts are rarely "bad" in regards to low drag ;-)

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [gralden] [ In reply to ]
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In Reply To:
This post just seems to be getting a bit rough as it goes on.

It's getting rough, because Kestrel's representative (Steve Harad) repeatedly pops in here, proves that he's paying attention, and seemingly deliberately ignores any relevant posts. Redo this exact thread, but with Felt, Cervelo, or Specialized, and I'm certain that Dave, Gerard, or Mark would be answering with real data and clarifications, instead of hand waving.
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Re: Kestrel Wind tunnel data [Andrew V] [ In reply to ]
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Andrew, these people (bike reps) do have real jobs and hanging out on message boards are more then likely not on the top of their lists of things to do during the day. I appriciate where you and others are coming from but Kestrel did not create this post (to toot their own horn), they are simple trying to respond when they can, just like all the others do when they have the time. Like I said, they will show more when they are good and ready I am sure.
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Re: Kestrel Wind tunnel data [gralden] [ In reply to ]
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He did find time to tell me that the data wasn't amateur, but ignored the quite simple question* I'd asked 4 times.

I appreciate that he probably has better things to do, but answering the most basic of questions about the testing would solve a lot of the problems.

*What speed the test was run at
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Re: Kestrel Wind tunnel data [zebragonzo] [ In reply to ]
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Gonzo, he might just be assuming that everyone knows that tunnel speed is 30mph for these kinds of bike tests, either that, or he does not like your name ... ;o), he hates zebras maybe.....
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Re: Kestrel Wind tunnel data [gralden] [ In reply to ]
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I realize that they didn't start this post, and that it's not their responsibility to constantly respond to it. There are my points:

1) If you competitors are spending the time to validate their data, be active in the community, etc., then it does become an expectation that, if you want to be treated on the same level, you will do the same.

2) Kestrel publicly released the graph. The data on the graph is suspect, and not well described. It is the responsibility of the company releasing the graph to provide adequate data to support it. It's not unreasonable to expect them to post a follow-up to the information, either as a press release, or some other way. They don't need to be directly answering our questions.

What Kestrel has done so far is similar to Ford providing an advertisement containing a graph of gas mileage, and claiming 70 mpg for the Focus. People would expect them to provide data supporting this claim (was this done in a vacuum? On the moon? With a strong tailwind? With all components removed except for the drive train?).
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Re: Kestrel Wind tunnel data [gralden] [ In reply to ]
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In Reply To:
Gonzo, he might just be assuming that everyone knows that tunnel speed is 30mph for these kinds of bike tests, either that, or he does not like your name ... ;o), he hates zebras maybe.....

I reckon he's just got a bit of a man-crush on AC and Tom! :-P
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Re: Kestrel Wind tunnel data [zebragonzo] [ In reply to ]
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I just finished a little internet cruise through several of the wheel/frame manufacturers sties and came across what was, basically, the same type of data presentations (did see a few notes on speed and lots of curvy lines). You boys should probably do the same so that you can level some more of your angst and chagrin at a wider cast of conspirators! I am glad that I am a poor teacher who rides a "slow and obsolete" frame while placing the emphasis on my legs getting me to the finish line. The way I see it, I only have to train a little harder and smarter to make up for the time lost to those multi-thousand-dollar world-best frames that hit the market every year. I may be wrong, but at least I'm not getting worked into a frenzy! (I can't believe I read "F*@# off" on slowtwitch!)

http://stlifeontherun.blogspot.com
Official Polar Ambassador
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Re: Kestrel Wind tunnel data [chemteach] [ In reply to ]
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In Reply To:
I just finished a little internet cruise through several of the wheel/frame manufacturers sties and came across what was, basically, the same type of data presentations (did see a few notes on speed and lots of curvy lines). You boys should probably do the same so that you can level some more of your angst and chagrin at a wider cast of conspirators! I am glad that I am a poor teacher who rides a "slow and obsolete" frame while placing the emphasis on my legs getting me to the finish line. The way I see it, I only have to train a little harder and smarter to make up for the time lost to those multi-thousand-dollar world-best frames that hit the market every year. I may be wrong, but at least I'm not getting worked into a frenzy! (I can't believe I read "F*@# off" on slowtwitch!)


Well...we here at ST hold manufacturers to a "higher standard" ;-)

http://forum.slowtwitch.com/forumfaq.html

Quote:
SCIENTIFIC DATA: If the data is merely a reprint from another website or publication, all that is needed is a link or a reference to the original source (and as much information is provided by the original publisher).
If the data is coming from you, as a private individual, simply do your best to explain your testing protocol and methodology. You should be prepared to answer questions to the best of your ability.
If the data is coming from a company that you work for or are otherwise affiliated with, you need to explain your affiliation to that company. And you also need to provide adequate information to support the data which your are presenting. Whether or not that support is adequate is up to the judgment of our moderators. One guide is that if the data was being published by your competitor, what would you want to know? Another useful rule is that you should never reply to a question with the following, "Call X if you have a question"; you need to be able to explain what you have presented. Otherwise, you can't post it. If you have any questions about information you'd like to post, our moderators are always available to answer questions.

...and here's the thread where Rappstar expounded on this when the "rules" were implemented:

http://forum.slowtwitch.com/...resentation;#1999873


Now then, I believe that the OP in this thread is not affiliated with Kestrel, and merely followed the first part of the rule. However, I think that once someone who IS affiliated with Kestrel starts responding in regards to that posting of data, perhaps the third portion of the rules should be applied?

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [zebragonzo] [ In reply to ]
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In Reply To:
In Reply To:
Gonzo, he might just be assuming that everyone knows that tunnel speed is 30mph for these kinds of bike tests, either that, or he does not like your name ... ;o), he hates zebras maybe.....

I reckon he's just got a bit of a man-crush on AC and Tom! :-P

:-)

In point of fact, however, not once in this thread has Steve replied directly to me (and I have really only asked one question).
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An open letter to manufacturers [ In reply to ]
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Dear manufacturers,

On this forum, we often see data which is poorly presented and lacking information necessary to make it useful. Occasionally, we see good data.

To start with Cervélo made many a believer by ensuring that technical questions were not left un-answered. Trek then published a good white paper and they were considered serious contenders in the world of aerodynamics. Since then Specialized have got in on the game and their data is respected.

What all these companies have in common is that they release information that is sufficient to allow us to see what the data actually shows.

There are some basic things, which, if you cover, will save a lot of time by answering them at a latter date and will generally give us lot far more confidence in your data:
1) Where was the testing conducted?
2) Test protocol. eg. “Measurements taken by sweeping from 20° to 0° yaw. Wheels rotating”
3) Wind tunnel conditions. Speed is the main info you need to share. It would also be nice to know air density.
4) Bike setup. You may have tried to set the bikes up in the same way, but did you measure from the BB or ground?

The following information needs to be provided for each piece of equipment you test:
1) Date and time of test
2) Equipment used (eg. Wheels – 2007 zipp 808 clinchers with GP4000S tyres)
3) Bike size
4) Number of repeats of test
5) A photo would solve a lot of problems here, although I realise this may not be that easy

I look forwards to seeing test data with details attached in the future.

Rob T
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Re: Kestrel Wind tunnel data [gralden] [ In reply to ]
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In Reply To:
Andrew, these people (bike reps) do have real jobs and hanging out on message boards are more then likely not on the top of their lists of things to do during the day. I appriciate where you and others are coming from but Kestrel did not create this post (to toot their own horn), they are simple trying to respond when they can, just like all the others do when they have the time. Like I said, they will show more when they are good and ready I am sure.
Steven isn't a bike rep. He's the president of Kestrel. And you'd be amazed at the number of companies where keeping an eye on the various forums is at the top of the list of things to do during the day. Actually, maybe you wouldn't be amazed. Just go look at the brands atop the Kona bike count.

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Kestrel Wind tunnel data [Tom A.] [ In reply to ]
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In Reply To:
Well...we here at ST hold manufacturers to a "higher standard" ;-)

That's right. No manufacturer may call any other manufacturer a "scl scntst"!

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Kestrel Wind tunnel data [Rappstar] [ In reply to ]
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In Reply To:
In Reply To:
Well...we here at ST hold manufacturers to a "higher standard" ;-)

That's right. No manufacturer may call any other manufacturer a "scl scntst"!

Exactly...only the riff-raff are allowed to stoop that low ;-)

http://bikeblather.blogspot.com/
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Re: Kestrel Wind tunnel data [zebragonzo] [ In reply to ]
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"2) Scientists use straight lines, marketing people use curved lines; unless you know how the data varies between two points, assume it's linear"

Actually it is as wrong to assume linear data between points (straight line) as it is to use curved lines. I would argue scientists would use dots and would leave then unconnected.
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Re: Kestrel Wind tunnel data [Trirunner] [ In reply to ]
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In Reply To:
"2) Scientists use straight lines, marketing people use curved lines; unless you know how the data varies between two points, assume it's linear"

Actually it is as wrong to assume linear data between points (straight line) as it is to use curved lines. I would argue scientists would use dots and would leave then unconnected.
Linearly interpolating data is SOP in science.
Last edited by: Andrew Coggan: Oct 19, 09 14:59
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Re: Kestrel Wind turnnel data [Rappstar] [ In reply to ]
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I agree with Rappstar on companies spending tons of $$$$$$$ on R&D and not taking the final step on packaging up the product with the correct supporting materials like whitepapers. I fight this battle all the time within my own company and more often than not, I get the fun job of writing the whitepaper on a variety of technology problems...and then having to stand in front of customers and analysts and speak to the points and get the hard questions.

Soooooo, I'll volunteer my to write the whitepaper for free provided that the raw unadultered experimental data is provided as input to the whitepaper. Steven can provide the Kestrel marketing spin, and like any whitepaper, the writer will be glad to map it to the hard data, provided that it can legitimately be mapped and that you can't drive a Hummer through the holes in the arguement.

All kidding aside, a agree with most of the posters on the thread. The 4000 looks at the surface to be an awesome bike. If it is aero "enough" and has the right look it can be marketed to anyone. You don't need the most aero bike in the market...that's just going to sell to the top 1% of the field. If you really aren't the most aero bike in the market (or the top tier of aero bikes), better to steer clear and focus on other attributes :-)

Having a bike that is reasonably aero, with data to back it up, ridden by some fast dudes to fast bike splits and looks incredibly hot will sell to the "fat part of the market" ...and frankly that is what that really matters in any business when it comes to revenue and profitability.

You don't need the best widget in the market, you just need the widget that lots of people will part with greenbacks for and want to be associated with. Now what do you have to do to make it happen? Do you need the best windtunnel data? I don't think so. 99% of triathletes could care less whether their bike came out top in the windtunnel or not.

I know guys on this thread do care, so you better offer them the data they are looking for, or focus the marketing on other early adopters who can influence the market in other ways.

:-)

OK, carry on with the regular programming.

Dev
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Re: Kestrel Wind turnnel data [devashish_paul] [ In reply to ]
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In Reply To:
I'll volunteer my to write the whitepaper for free provided that the raw unadultered experimental data is provided as input to the whitepaper.
Now why should they take you up on that offer when they could pay many an MD to write up the results without ever seeing the raw data? ;-)
Last edited by: Andrew Coggan: Oct 19, 09 14:58
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Re: Kestrel Wind turnnel data [Andrew Coggan] [ In reply to ]
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Just like I tell the engineers in my company....show me the data from the lab so that I can put the marketing spin on it...but I want to see the data, cause I can't market it without believing it myself. And I do have to stand in front of people and defend it beyond what is written, so it better be real, or my credibility is toast, and I'll never win that customer over again and if I can't win the customer or help the sales guy do it, all of our paycheques are toast. In the end, customers pay our paycheques, not executives :-)
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Re: Kestrel Wind tunnel data [Andrew Coggan] [ In reply to ]
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"Linearly interpolating data is SOP in science"

Guilty as charged of thinking like the engineer that I am, then!
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Re: Kestrel Wind turnnel data [devashish_paul] [ In reply to ]
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In Reply To:
...The 4000 looks at the surface to be an awesome bike. If it is aero "enough" and has the right look it can be marketed to anyone...Having a bike that is reasonably aero, with data to back it up, ridden by some fast dudes to fast bike splits and looks incredibly hot will sell to the "fat part of the market"...

...and to be fair, (and as I told gregclimbs, The Privateer, and sharad in the Kestrel booth at Interbike) I personally think that the 4000 is "drop dead sexy" looking.

However, there's nothing more frustrating than a knock-out looker that doesn't perform up to snuff...we're just trying to make sure the performance matches the "looks" ;-)

http://bikeblather.blogspot.com/
Last edited by: Tom A.: Oct 19, 09 15:07
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Re: Kestrel Wind turnnel data [Tom A.] [ In reply to ]
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I reckon he's just got a bit of a man-crush on AC and Tom! :-P

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...and to be fair, (and as I told gregclimbs, The Privateer, and sharad in the Kestrel booth at Interbike) I personally think that the 4000 is "drop dead sexy" looking.

sharad does know that you were talking about the bike when you said drop dead sexy...right?
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Re: Kestrel Wind turnnel data [zebragonzo] [ In reply to ]
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I reckon he's just got a bit of a man-crush on AC and Tom! :-P

In Reply To:
...and to be fair, (and as I told gregclimbs, The Privateer, and sharad in the Kestrel booth at Interbike) I personally think that the 4000 is "drop dead sexy" looking.

sharad does know that you were talking about the bike when you said drop dead sexy...right?

I hope so! He's a big guy! (Well...bigger than me, that is) ;-)

http://bikeblather.blogspot.com/
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Re: Kestrel Wind turnnel data [Tom A.] [ In reply to ]
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See, you guys are critical consumers. Most just go for the knock out looker, even if she is high maintenance, can't perform and might have to be traded in not to far down the line due to the high maintenance factor. But lust is only skin deep as we all know...
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Re: Kestrel Wind tunnel data [gtingley] [ In reply to ]
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What kind of difference does that translate to on a TT? Seems to me that when Zipp is calculating for their wheels they use approx 3sec / 1 gram, if so, that is a pretty big difference. Or am I way off base?

Kevin
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