Originally Posted by
TiHabanero
I think what I am after is how meaningful are aero dynamics of a frame when put to the test and all the elements of riding the road are incorporated. It is assumed it makes a difference, however it has not been proven outside of a laboratory environment. I know aero wheels make a difference as we comparison tested them over several time trials on the same course with similar weather conditions. Results were consistently huge. If it can be done with wheels, it can be done with a frame. Timed results will be small so It might be difficult to find consistency.
Oh, that. Years ago Tom Anhalt field-tested a 2001 or 2002 (?) Cervelo P2K (already a pretty aero TT bike for the day) against a 2007 or 2008 Cervelo P3C. It turns out that when holding the wheels and his position and clothes constant, the CdA of the P3C at zero yaw was about .023 m^2 less than the P2K. This turns out to be almost exactly what was measured in a wind tunnel. The predicted time difference based on this estimate for him would have been just a tad more than 2 sec/km in a TT, and was confirmed later that year at the SCNCA TT championship course, where under slightly worse wind and air density conditions but almost exactly his same average power, he improved his time with the P3C by something like 1.8 sec/km on the P3C vs. the P2K.
So there is your real-world racing difference. There was
an insanely long thread on Slowtwitch where a million questions and criticisms were asked (I think the criticisms were roughly equivalent to the one above, and I answered them in 2008 so there you go). That was for two TT bikes. The difference between a road bike and a TT bike would, of course, be larger.
The bottom line is that you don't often hear about "real-world tests" not because they're not done, but because the results you get from the field and wind tunnel tests tend to validate each other.
That said, if you're interested in total drag (as you should be) as opposed just to aero drag, you have to take into account rolling resistance, which you can't do in a wind tunnel. In a wind tunnel you only measure aero drag (obviously) so, for example, narrow tires always do better than wider tires. However, in field tests we can look at total drag on varying surfaces, and that's when you can determine that there are instances where you can trade off some aero drag for better rolling drag and end up lowering total drag. I've done that for a couple of the recent world hour record attempts, and for some road race championships. As mentioned above, I've done a little bit of work with Olympic pursuit teams. That worked well, and In another Olympic test, in the run-up to the 2016 Olympics, the Swiss MTB team tested various tires at various pressures using my method, and it worked out for Nino Schurter.