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i saw that the other day. i have a set of Rolf Prima Vigors and was wanting to get rid of them, but after see that, I'm thinking about reconsidering. Of course, it's their own data, but it's convincing nonetheless. I would love to see an independent review.
 

· wheelbuilder
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They just gave everyone no reason to buy their carbon wheels. Why spend the money when you can get the SLs that are the most aerodynamic is typical 0-15deg conditions? That looks like a bunch of BS and doesn't conform with any of the other tests I've read. Anyone who thinks that a 34mm rim is more aero than a Zipp 404 is smoking some good shite.

-Eric
 

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jmess said:
Here is some interesting test data provided by Rolf showing wind tunnel tests done on a variety of wheels.
Can anyone explain why these data show drag increasing with yaw from 0 to 15-20 degrees while every other data set I've seen shows drag decreasing? This seems suspicious.
 

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wiz525 said:
do you have a link for any of the other data? I'm getting rid of my Rolfs and want to look at some of these data before I buy. Thanks.
For the effect of yaw on drag, the one I know off-hand is zipp.com. Before anyone dismisses this as self serving, I'd point out the results have been confirmed many times by independent tests (I just can't remember the URL's).

As a guide to buying, Tour magazine has published data on a range of wheels.
 

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wiz525 said:
I would love to see an independent review.
Hell, I would love to see an X axis that actually starts at zero. Then it would be apparent that there is almost no difference in the results except for a R-Sys and Krysium SL. After, that, buy the cheapest and prettiest.
 

· Former Roadbikereview Editor
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What does this data mean??? How fast is the rider going? What is 280 grams of drag and how much does it affect speed?

Is there any doubt that Rolf would be top dog in the Rolf study?

I have a really good French aero data somewhere. I'll dig up that link of mine.

fc
 

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iliveonnitro said:
Why would drag decrease as yaw increases?
I could speculate, but I'm not really sure. It must involve a decrease in pressure drag overcoming an increase in skin friction, but I haven't seen anything showing exactly how the changing flow character at non-zero angle of attack results in a decrease in the total stress over the wheel surface.
 

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I know aero wheel testing is very difficult to conduct, but those Rolf wind tunnel results are confusing. What speed is used for testing, and where are the data for Watts at given speed?
Independent testing I've seen includes Tour Mag Sep '05 and June '07 as well as:
http://rouesartisanales.over-blog.com/article-15505311.html

FWIW- Zipp also has test data on their web site.

Essentially all other test results I've seen indicate that aero drag is generally decreased by increasing rim height and bladed/oval spokes vs round.

Most of the Rolf drag results differ markedly from other independent testing. In agreement with most other tests, Rolf found minimal differences between wheels at zero yaw angle, and the relative aero INefficiency of the Ksyrium design at all yaw angles. Other than that, however, the results are curious. They indicate that Rolf's Elan (23mm rim/round butted spokes) is more aero than a Zipp 404 (58mm rim/CXray oval spokes) at 10-15deg yaw. Even within the Rolf product line the data don't seem to make sense. The 34mm Vigor SL outperforms their own 58mm TdF at all data points except 20deg yaw.

Rolf may make some nice wheels, but wind tunnel test results???????
 

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Discussion Starter · #13 ·
I was just surfing their site and found this. I ride a set of their wheels but I am not trying to promote them. Just wondered if this type of testing holds any real water. I figured the really smart people on this forum could explain the physics behind the results or lack of.
 

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iliveonnitro said:
Why would drag decrease as yaw increases?
This is only true of rims that have some depth to them. Supposedly, the aero shape produces an airfoil effect which provides a little relative thrust in the forward direction. For a rim like the 808 (82mm deep) the low point in the drag vs yaw curve is ~13 degrees. If you are TTing you will rarely have a greater yaw than this even on a windy day.

The Rolf data is surprising in several aspects. Since it disagrees with the other published data I've seen, I'm pretty skeptical. I'd love to see more field test data from people with power meters though, since this is more indicative of the real world. Unfortunately, varying conditions in the real world make testing there very time consuming and tedious if you hope to get decent accuracy.
 
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