Given the amount of time that I have spent in the wind tunnel testing athletes and my experience with Jim at ERO, perhaps I do understand it a bit more. It would do well for you to take the time to understand it also. Most of the watt savings stated are based off the ROT that goes .005CdA~=.5sec/km~=5watts. This is at the typically tested tunnel speed of 48kph.
A .005 reduction to CdA at 48kph is almost 7 watts, But it takes a rider ~400 watts to go that speed with a starting CdA of .25. A rider capable of pushing 200 watts is going to be looking at a savings of a bit less than 3 watts.
As others have said when someone says something saves X you have to look at the specific conditions and speeds in which they were tested. CdA completely eliminates the guess work as it is a relative constant and scale pretty linearly.
trail wrote:
Ex-cyclist wrote:
CdA doesn't change appreciably with speeds that cyclists ride. Watts on the other hand can vary quite a bit.
There are CdA figures, near the bottom. Though I find Watts more useful.
Yeah, I get it. But at least for me differential Watts are a more accessible mechanism for understanding the magnitude of effect.
If he had just reported the CdA differences of 0.006 (which is roughly what it was), I'd have to spend some time converting that to something else.
Reporting that it saved 6W @ 200W is immediately accessible.
Maybe you've learned to have a more intuitive sense of CdA, but I think you'd be in the minority there. We spend all day looking at power meters. Except Jim, and a few others. I do my own Chung testing, but even then I like to look at Watt differential at the speeds I'm going.[/quote]
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