wens

https://www.speedplay.com/index.cfm?f...slipperypedals
https://cozybeehive.blogspot.com/2009...speedplay.html

This is all I could find about it, and I couldn't find the data plots. Do you happen to remember where you saw them?

ZeCanon

From what I've seen, a 21mm Vitoria is not the ideal tire, so no it did not necessarily help drag values.

Nope just apples. I was noting a trend, not making a direct comparison. Wider rims tend to be wider all around (not just at the brake track), and tend to handle better in crosswinds. This is based on riding more more than well over a dozen 50-100mm rims (tubular and clincher) in the last few months.

Better tire shape (and thus ride quality/handling), often better aerodynamics. As I have posted twice now...

I certainly hope the quotes aren't implying a lack of objectivity on my part.

tanhalt

I thought it was on the Speedplay site itself...but maybe it was somewhere else. I do remember discussing it with a bike industry aerodynamicist (i.e. someone with an actual degree in the field and with familiarity with the tunnel used) at Interbike and both of our initial reactions were along the lines of "offset error"

tanhalt

As compared to a 23mm Vittoria though? Are you saying that if you were to put a 23mm Vittoria on there it would result in lower aero drag?

In any case, what's the logic in testing a wheel with a tire size on it that voids the warranty?

waterrockets 

Yeah, that's what I'm thinking.

Yeah, I guess it all cancels out with the rotation. If we rode around on paddle wheels in still air, clearly the paddle at the bottom isn't adding any air resistance, and a wind tunnel replicates this because the wheel would be spinning to match the air speed.

That is an interesting thought though, considering drag at, say, wheel/wind speeds varying between 26mph and 32mph during the test. And some gusts.

A gust is particularly interesting, because if it has any yaw at all, the yaw will change as the gust accelerates. So the rig would have to spin while the fan blows harder, then un-spin as it slows. For head winds, it would be a case where wind speed would go up, but wheel/bike speed would go down.

Nate552

I've got a HED tri spoke with a Bonty aerowing clincher mounted to it if you want to take it with you. You're also welcome to my Singer 9 C2 (2010 version) to try some different tires.

Racer Ex 

Road trip to NC with me?

Nate552

Sure, it'd be fun to compare the A2 tunnel and the ATM tunnel. BTW headed back to the tunnel Nov 15-16.

wens

The comments on the blog make it seem like something was on the speedplay site but was later removed, so I'm guessing that's what they were talking about. Wish I'd seen it, sounds like it would have been interesting.

tanhalt

Well, another way of looking at seeing if it passes the "smell test" is to calculate the change in frontal area caused by the 3 hole vs. 4 hole configurations (the 3 hole has a thin adapter plate) and compare that to the difference they claimed to measure. That thin plate would have had to DRAMATICALLY change the Cd to affect the CdA by that much since the change in A was nowhere near enough. I'm not buying it.

rruff

The data I looked at from a rider at Texas A&M showed at least 2% scatter, though some claim 1% is possible. Tunnel time is so expensive that it is tough to do a lot of repeats to bring down the uncertainty level.

Now, considering that the wheels are ~10% of total drag, if you are comparing wheels with a rider aboard, you are looking at 10-20% uncertainty... really too much to tell anything.