Thanks for the data!

I guess that the 82 and 108 lines refer to the zipp wheels?

Hmm. Well, I guess that explains why initially only the Stinger 6 and 82 mm data were presented...

If the Jet 90 C2 I bought last month is comparable or close to the Stinger 9 this data just made me a very satisfied customer.

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People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf. George Orwell

so the sub9 is not the only negative drag wheel.....it looks like the stinger 9 goes below the x-axis at 12.5 yaw.

Once again I'll say that data like this becomes important when we start racing in wind tunnels....

Hell, I would bet that nto many people on ST (Ok, Dr. Coggan you would) understand the impact or perhaps lack therof of the data you're presenting.

Once again I'll say that since I started racing in a vacuum I can safely ignore data like this.

Outer space racing is a blast, you should try it! It's the next Big Thing.

"Hell, I would bet that nto many people on ST (Ok, Dr. Coggan you would) understand the impact or perhaps lack therof of the data you're presenting."

That's a fairly disingenuous statement.

At least the new logos look cooler than the older ones....

I wouldnt bet on seeing any data any time soon.
Seems to me the Jet C2's are selling just fine (hell, I just bought a 60/90 wheel set) and HED is having trouble keepoing up with demand, so there is no need to actually provide any data...

I will however, happily stand corrected ;)

what aerobars are those peeking in from the top of the side pic of the wheel?

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Trek Speed Concept 9.9

I wonder if the Jet C2 90 and Stinger 9 models perform similarly, aerodynamically

How so?

If I am wrong, please let the denizens of ST accurately explain what the real world explanation (not-in-a-wind-tunnel) of what yaw angle, grams of drag, etc mean and the impact it will have on their race times, efforts, and rest....Go ahead.

Much like those who profer medical advice to those who ask, there seems a fair amount of aerodynamic interpretation bullshit that flies from the keyboards of many a ST poster. Most of these folks' knowledge of aerodynamics could fit into a thimble and their knowledge base is merely what they are told by reps, ST'ers, or read off of some marketing material.....

I stand by my comment.

Bob

You can win yourself a new HED Stinger wheelset by making closest guess of Bjorn's SavageMan bike split.

There are not a ton of guesses, so this is about the best chance of winning a major prize that you will ever encounter.

http://www.savagemantri.org/Bjorn.html

   
Well, the R.O.T. that Dr Coggan coined, is that a .005 CdA improvement is worth ~20sec over a 40K TT.

So, for example, going from .245 to .23 would net a 1min faster 40K TT.

Well in the real world, which also has wind, just like a tunnel does, less grams of drag, at a given yaw angle, means you will go faster.

There are various online references, not affiliated with any wheel maker, which have done the math showing how much time is saved, for a given power output and drag reduction.

What exactly are you skeptical about? Do you think the "real word wind is somehow fundamentally different than wind tunnel wind, such that no time would be saved by having less drag?

I mean, people have down real world testing on these things too...

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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

I'm not skeptical at all, but all of this data lacks one very important item: The Rider.

You can say all you want about the wheel and the benefit it MIGHT bring, but if the rider is set up improperly, has an odd pedaling style, or is simply unfit, these gains will not be seen. I think I've read that 75% of all drag is created by the rider, so if they're causing more drag, wheels aren't going to do pooh.

Bob

If I am a rider whose position Causes Y drag, and my wheels and bike create X drag, my total drag is X+Y.

If I reduce X, there is less total drag no matter how good or bad my body drag is.

There is a valid point, in that a rider might work on their position first, since that will be a cheaper improvement. But either will be an improvement.

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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

 
Thanks Jason...are the additional 2 plots also with a 21C Vittoria CX?

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http://bikeblather.blogspot.com/

I hate to say it...but my "gut feel" is that when compared with appropriate sized tires, the C2 version of the Jet 90 will actually have slightly higher drag than a regular Jet 90...especially at lower yaw angles.

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http://bikeblather.blogspot.com/

 
...oh, and I forgot to ask: Do you know if these plots are "normalized" to a standard temp and pressure, and what wind speed are they for?

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http://bikeblather.blogspot.com/

They look like heds, and the jeans look like 501s :)

Do you have a point here or just trying to be argumentative? If you take the same rider with their bizarre pedaling style (what does that mean aerodynamically anyway?) and weird position and put wheels on their bike that have less drag...that rider will go faster. Unfit? Like most of your comments here this is a totally ridiculous non-sequitur.

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The Hed website copy describing the C2 implies that it has lower drag, but I noticed that there are notably no drag numbers supplied.

Hed does supply drag numbers for both the older Stinger 90 and for the Jet 90, showing very similar drag for the two wheels but the Jet is slightly lower.

This thread has a zip-supplied chart that compares the 808 with a "H90" wheel, which I think is the Stinger 90 but I'm not sure, I didn't read the entire thread. It shows the two as being very close but the 808 being a slight bit better.

The curve between that chart and this one for the 808 look a bit different at high yaw angles.

FWIW.

Thanks for posting-interesting stuff. I guess there are two thoughts that come to mind:

1) I really don't see many people going for the 90 over the 60, particularly for a front wheel. There just isn't enough of a difference to make up for the extra side forces (and I say this as someone who's a big fan of using the deepest wheel possible).

2) I realize you're just presenting the data, but at some point, the 808 data needs to be explained. The drag curve doesn't resemble anything other data out there, including the data presented by you earlier (the Trek/Hed data). Is it a clincher, by any chance?

Precisely what I was getting at: why do the "82" and "108" data differ so markedly, when all other evidence points to there being a relatively small difference between the two wheels?

A couple of thoughts come to my little pea brain... First won't drag be a function of both wind and speed? If so, I think we need a three dimensional graph. iow, the best wheel at 24 mph might not be the best wheel at 26 mph. But, I'm speculating...

Second, I'm not sure that it's valid to add the rider's drag to the drag of the bike and the wheels. My guess is that the wheel tests we've seen are done in "clean" wind; not the turbulence that is churned by the rider's legs and the airflow over the back. It also seems like front and rear tests would be necessary.

Finally, it seems like all of this could vary significantly among individuals. So, we'll likely never be able to find the "right" answer. So what this is, is a way of saying, "Mine's better than yours", when the only mine's better that counts is the results!

Did I just concoct a long winded version of HTFU? ;-))

Meaning that at lower yaw angles which is more of a front on view of what would be a wider rim (Jet C2) would yield more aero drag. Yeah that would make sense. Question is though whether the lower RR would negate that deficit and as the wind tends to be more times at yaw angles not at directly face-on 0 yaw then wouldn't the overall be a faster wheel? Just curious.

Thanks
Andy

Well...that depends on the tire, I think. AFM did tests on low Crr tires (Bonty RXLPro 23 and VF Record 20) and found little, if any, appreciable difference in Crr for a given tire on varying rim widths. Based on what Al shared below, I'm not seeing where the >10% reduction in Crr is since his data implies ~2-3% at most:

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http://bikeblather.blogspot.com/

When was the last time you rode into a wind that had zero yaw?

FWIW, last year we tested a Zipp 999 wheelset against a competitor's set of wheels on my wife's bike with her aboard, and the results were consistent with what you'd predict based on wheel-only tests.

Thanks for weighing in, Dr. Coggan. I value your input.

While this is clearly a selling point of the bicycle that you tested (the P3c in track mode), I don't know if your data is representative of the different configurations we're likely to see around here with respect to rear wheel gap and the overall design of the rear wheel cutout. As Cervelo states - no cutout is better than a bad cutout.

Chris

Hello,

I have a few points to bring up. First, to the person who said "if the rider has X drag and the wheel has Y drag, then the system has X+Y drag", this is actually completely false. Aerodynamics is very complex, and interactions are very important. We could consider the front wheel alone (in isolation from the drag of the rider/bike system) only for supersonic flow... if you have that situation, then you are probably not needing to worry about shaving a couple extra seconds off to win.

Anyways, with regards to the pictures and data that were posted, I have several concerns:

1. The coordinate system of the force measurements is not specified. I have seen work done where the drag was reported in wind tunnel axes, not the bike axes. (When I ride my bike at least, I try to keep it pointing in the direction that it is moving.)
2. There are no error bars on that data. How significant are those fluctuations in drag with yaw angle?
3. The set up is not very clear in the picture and it is not well explained. The massive metal cylinders that make up the stand that you can partially see in the picture are worrisome. We don't even know if they were "into" or "away" from the wind. In either case, they are large enough and sufficiently blunt that they might cause systematic measurement errors.
4. Grams of drag is entirely meaningless. Ignoring all of the other issues, those values would be extremely good for 100 mph wind and extremely bad for 10 mph wind. The numbers could be a) normalized using the relative headwind velocity (in the frame of the bike, ideally) to get a drag coefficient area, or b) the wind speed could be reported. The former is actually more meaningful.
5. As I previously mentioned, a wheel alone test is really only meaningful for the case where you crash within sight of the line and your wheel travels to the finish by itself. There needs to be at least a bike there to make the data meaningful.

Bottom line is that the data, as presented, is not trustworthy. There is not even sufficient information available to evaluate the merits of the test.

Regards.

That picture of the wheel is from the HED display at Eurobike, NOT from the windtunnel test...

Once upon a time I was involved with developing aircraft, and I can tell you that yes, the real world and the tunnel are very different.


Most of the things I see on ST related to aerodynamics have me scratching my head, which is why I rarely post on the subject.

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Yeah, it's a great bike but the engine needs work.

 
Actually it isn't completely false, as others have pointed out, with bicycles it does happen to work out pretty close to X+Y

Anyway it was a silly simplification to rebut a silly argument someone else had made, which you either didn't notice or didn't care, because you wanted to be like that guy who raises his hand in college, not to ask a question, but to point out how much he knows.

Thanks, for letting us know that aerodynamics is complex.

Also, fyi, the wind speed and normalization used is noted earlier in the thread.

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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

And they use wind tunnels to develop aircraft too, even though an aircraft would be far far more sensitive to variations between the smoothe regular airflow of a tunnel than the turbulent air of the sky, they get useful data from it.

yet we are to believe a wind tunnel is meaningless in evaluating bike wheels!

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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

I'm sorry my post came across to you as it did, but I believe you have misinterpreted it. I have some experience doing wind tunnel testing on this equipment, and enough to know that the X+Y simplification does not really work out all that well.

As to the comment about the stand, that is good to know. I'm glad that stand wasn't involved. I should have looked at it more closely. At any rate, the point that the stand can really influence the data still stands.

the wheel stand is tared out of the final numbers.

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Andy Tetmeyer (I work at HED)

Hi Andy,

Thanks for the reply. Part of my curiosity was the actual geometry of the rig. Is there an actual paper on the test by any chance?

Ok, gotta say...wow.

1. The data was measured giving drag along the translational axis, not the wind tunnel axis. To give data otherwise would be meaningless (Nimble's weird "Total Drag" numbers). No reputable company would do otherwise, and Hed is a reputable company. If you'd been paying attention to previous aero tests and discussions you'd already know this.
2. Consistency of testing is pretty impressive with wheels on multiple runs as long as they are made in the same direction (i.e. going from 0 to 30 degrees and back rather than 30 degrees to 0 and back to 30). There's some argument as to whether you should start the sweep at 30 or at 0...Zipp advocates starting at 30 iirc. Also iirc the repeatability is within a couple of grams for non-rider stuff. It's tough to get a rider to be in exactly the same position for hours on end.
3. Give me a break. That is the DISPLAY AT A TRADE SHOW. Does it even look like a wind tunnel? Why would they put two wheels next to each other like that? Yeesh.
4. Grams of drag at a given speed is how you calculate watts. It's simple physics, I'm not going to give you a physics lesson to figure out how to calculate it. It just so turns out that 30mph (or 25mph for some tests) is almost perfectly scalable down to 10mph because 30mph is pretty darn slow in terms of aerodynamics. You just aren't going to see dramatic shifts in airflow patterns at these speeds. They test at 30mph because the forces are high enough to stay well away from the tolerances of the measurement equipment.
5. This is a ridiculous statement. You are essentially saying that the wheel's aerodynamics is irrelevant unless it's not on your bike. There are thousands of hours of windtunnel tests (some from posters in this thread) that show your statement is 100% completely wrong.

And regarding X wheel and rider Y = X+Y, in the case of a front wheel this is reasonably correct. See Andy Coggan's post above. We all know that the rider's legs, bike frame, etc all have a big effect on the performance of the rear wheel, but not a lot on the front wheel. Ideally you'd take your wheel/tire/bike/self combination into a windtunnel and spend $3000 to get all of it tested and your position optimized. Since I don't have that much money I do field tests and look at data like this to make intelligent decisions about my wheels.

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Where have I missed the testing data on the Jet 90 C2 and the Hed Jet Disc? I thought these were promised but have not, to my knowledge, materialized.

.

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Bob C.

The "science" on any matter can never be settled until every possible variable is taken into account.

I must admit that I have only been to Slowtwitch a few times, and I do not pay attention to all of the threads about aerodynamics. I have seen a few, but

To some of your points:
1. Yes, bike axis is the correct way to do it. Not everyone actually does it that way. It's a good question to ask.
2. The odd hysteresis issue you bring up is worrisome.
3. I already said that I should have looked closer at the picture. As an explanation, I was extremely tired last night. Obviously, I should have looked closer.
4. No. Giving the force without saying what speed it was calculated at is meaningless. You can give an Cd or CdA, and it will scale to other (reasonable) speeds. I don't see anywhere that it says 30 mph, but then, I wasn't there, and perhaps you were.
5. No. Read the statement again. You understood it wrong.

Right, and in case you all don't realize it, I am not saying that the data is wrong. What I am saying is that there is not enough information there to make a compelling case for the accuracy of the data. I am quite curious if there is a paper which addresses these issues, because then an informed look at the data can be made. I was legitimately interested in finding out the answers to those questions, but this seems to be very closed to such inquiry.

Gosh, I wonder what makes aircraft and bicycles so different:

http://www.humankinetics.com/...U3r8V2m67Tjay3JK8nj2

(Note: reprints available upon request.)

To expand on that: the only case/place where there seems to be evidence of significant bike-rider interaction is between/aft of the rider's legs. For example, the Trimble monocoque frame (which, like the new Fuji, was quite wide at the level of the rear brake) tested quite well without a rider but poorly with a rider, and beam bikes seem to perform quite well (although not necessarily better than well-designed double-triangle frames). OTOH, when testing aerobars as part of Project 96 Jim Martin found a very high correlation (i.e., R = ~0.9) between measurements made with and without a rider, no one (to my knowledge, anyway) has been able to demonstrate that the performance of a wheel such as the HED3 is really dependent upon the spacing of the fork blades, etc. Thus, the belief that one should ignore wind tunnel data from bicycles or parts of bicycles tested without a rider is, in my opinion, rather myopic.

It is? I asked about it...but I don't see any reply anywhere.

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http://bikeblather.blogspot.com/

The search function here and on biketechreview.com (forum run by the guys that run the San Diego Low Speed Wind Tunnel) will help tons in finding out the background of how bikes are measured and the basis on which we are discussing this set of data. Regarding your items:

4. Based on a bunch of historical data I'll go out on a limb here and say it was normalized to 25mph. Most of Hed's previous data for 30mph were listed starting at 0 deg yaw around 180-190g, which makes sense that this is around 120-125g at 0 deg yaw. These are pretty much the only two speeds ever used to display data.
5. You essentially said the only time aerodynamics of an individual wheel matters is if it's no longer attached to your bike. Andy Coggan's two posts on this very thread (along with thousands of hours of wind tunnel testing) shows that solo wheel testing is pretty darn well correlated to testing on the bike. There are obvious exceptions such as on funny bikes like the Trimble that Andy mentioned and of course the rear wheel has all sorts of issues with flow around the legs, etc. If you want to argue with Andy about it...good luck!!!

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Ummm... I don't think so. I believe that they are hired by the LSWT to help when cyclists come in (if you want them there). Dave Sanford runs the tunnel and is an employee of the San Diego Air and Space Technology Center.

http://lswt.com/contact.php

g

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greg
www.wattagetraining.com

FWIW, last year we tested a Zipp 999 wheelset against a competitor's set of wheels on my wife's bike with her aboard, and the results were consistent with what you'd predict based on wheel-only tests.[/quote]
And i think this is a lot more convincing. Showing that there is a difference even after you add the drag created by the rider creates a much more convincing argument to buy (i think).

Of course, you wouldn't want to do this if your wheels show no difference in this sort of test.

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mckenzie

Picky semantics. With the change in name I'm not sure if anything else has changed out there. But the measurement quality is likely to remain the same, and more importantly, just as relevant to the real world as it has been. Besides, how often have you known a website to have the wrong contact info? Heck, our company still shows "current product" that was discontinued 5 freakin years ago!

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Hello Andrew,

Your point is well taken, but I disagree with you in this case. Particularly in the 10-12.5-15 degree range for this particular test, the absolute magnitude of the measured force is very small, and the addition of a bike to the system has the potential to qualitatively change the results.

Triguy42, I did attempt to add some humor to the last point in my original reply. I apologize. The bit about the wheel crossing the line was an exaggeration meant as a joke; clearly, I was not successful there. I was not saying that front-wheel alone data is completely useless, but it needs to be treated with care. I have seen some interesting interaction effects, particularly at high yaw angles; I feel very uncomfortable drawing any strong conclusions from the data presented here.

Actually, the slower a rider goes, the greater positive impact of aerodynamic equipment. So if one assumes this fat, odd-pedaling, badly set up rider of yours is relatively slow, then the effects of good wheels will be that much more dramatic in terms of time saved.

Yes, I know you will scoff at this because it's counter-intuitive - and, frankly, I'm fine with it if you don't believe me.

I don't doubt your assessment, but frankly I don't care really. There are so many who think that you can buy the best bike, best wheels, best everything and suddenly you're a FOP rider. Sure, all of that might help, but in the end it's nto about the bike...

And, since you may think I am merely trashing ST'ers, I say the same thing about golfers too.

Bob

"There are so many who think that you can buy the best bike, best wheels, best everything and suddenly you're a FOP rider."

Really? You asked them?

C'mon. People aren't as stupid as you're making them out to be. Some ask some really crazy, newbie questions...but most are reasonably able to comprehend the simple concepts once explained. People want to know what is the best stuff out there. If the laymen out there sometimes struggle with the vocabulary, and then find out that their initial assumptions about some concept don't hold up to the science...well...that's to be expected.

Except, of course, for you, since you seem to be so damn smart about EVERYTHING.

I don't know diddly squat about golf...but I know that you could hand me Tiger's clubs and I'd still shoot 100+. I'm pretty sure the people asking questions about wheels this or frames that also realize that we could hand them Macca's or Fabian's bike but they wouldn't suddenly be winning IMH or Worlds and Olympic TTs.

DUH!

It must be exceptionally difficult for you living in such a dumbass world.

Jesus dude I hope you're not into sales because you need to work on your people skills.

My point is this: Golfers and ST'ers alike think that by buying the best shit, they'll be magically faster or better. Aside from the theoretical application of better aerodynamic equipment, not one person has disagreed with that statement. I made a statement based upon anecdotal evidence gather in races.

For instance, I've seen people in races riding a P3C with 40mm of spacers AND a high rise stem with a Zipp 999 wheel set up going 13 MPH. Additionally, I've seen people with about $7500 in golf equipment shoot 130 and blame something other than a bad swing.

I did not attack anyone on this forum, nor did I say a disparaging remark about anyone in particular. If, however, you'd like me to insult your dumb ass, as you did me, great I can do that, but I don't want to make you cry.

Bob

not really (picky part) - one guy is there for every run the tunnel sees (and gets the mindshare of all the testing - perhaps learning things that would then be applicable to bike testing from non-bike testing) while the other pair is there for bike testing only (and not all of that either).

wanna guess which of the above designed the much discussed fuji bike?

I dunno if what I wrote above is still fact or not, but it is the way things were when I talked to Dave last year.

I was not questioning the validity or experimental method of the data (which hasn't been disclosed - so kinda hard to challenge :) ).

As the current-ness of any website...dunno how to respond to that... :D

g

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greg
www.wattagetraining.com

Actually, buying the best shit is a very successful strategy for "magically" going faster (the hard part is identifying what actually is the best shit vis a vis the most expensive shit). Aside from the logical and analytic evidence, I can share quite a bit of personal anecdotal evidence about how good equipment selection has allowed a very much run of the mill rider (me) to get some results way beyond his ability. A few years back, before everyone got the TT bug and started shopping, I had a TT setup that was *so* good compared to what everyone else was riding, I could show up to a TT out of shape and be in the money anyway. I used to loan it to my teammates and friends - whose first ride on it would be to roll to the starting line - and they would ride personal bests on it (and sometimes beat me, on top of it). And I'm not telling you anything about the frame or any of the components other than to tell you that without wheels I managed to get the whole thing built up for less than $1k, with pretty much all of it coming from ebay.

In Reply To

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For instance, I've seen people in races riding a P3C with 40mm of spacers AND a high rise stem with a Zipp 999 wheel set up going 13 MPH.[/reply]
That's not a good example of buying the "best shit" - that's buying the most expensive shit. If you're making the argument that disposible income and bad decision making are somehow correlated wrt gear purchases, I'm inclined to agree with you.

I think the saying should go "Lies. Damn lies. Statistics. Wind Tunnel test results."

Determining the best is the most subjective exercise in the world. The best bike for me is a P2C due to the head tube height and biomechanical issues with my hamstring. The best bike for someone else might be a P3C or even a Specialized or a Trek...

But, yes, my larger point is that people equate buying the most expensive stuff with benig the best stuff and thus that which will make them faster and better. There is a guy at my LBS who has a Pinarello Montello FP3 (Or whatever the uber bike is) and he equates that with the best bike because it is the most expensive. All tolled he dropped on the order of $15,000 for a TT bike with a whacked out setup to make him comfortable (risers, tall stem, etc) and has never sniffed the podium once....

Bob

Fast wheels are fast wheels, period, and tunnel info is good information (probably the most valuable and pertinent information available to you and me, actually) to use when you go shopping for wheels. Being a misinformed luddite is every bit as sinful as being a misinformed spendthrift. And I believe this thread started on the topic of how effective these new Hed wheels seem to be. If you want to start a new thread making fun of dudes who spend their money stupidly, I'd be glad to join you - but we should definitely keep that discussion out of this thread.