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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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this quote from Steve Harad (bold added)?

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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...
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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/
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Re: Kestrel Wind tunnel data [Dave Luscan] [ 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.

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...
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Re: Kestrel Wind tunnel data [zebragonzo] [ In reply to ]
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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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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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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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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...


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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. :-)
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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.
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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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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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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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"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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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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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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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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