Originally Posted by
echappist
Also, what about savings at 20 and 25mph? i know there's a equation, and it's somewhat linear w.r.t. to ground speed (or is it)
Drag is just a squared function. Nothing tricky. Mr. Bernoulli said so.
x = speed of interest (mph)
Dx = Power at speed of interest (grams)
D30 = Power at 30mph (grams)
Dx = D30 * (x^2/900) (FWIW, 900=30^2)
also:
x = speed of interest (mph)
Px = Power at speed of interest (watt)
P30 = Power at 30mph (watt)
Px = P30 * (x^3/27000) (FWIW, 27000=30^3)
This will give you the aero side of the equation. There will be a rolling resistance component as well. My guess is that as speed goes up, the rolling resistance gets kind of overpowered by aero, but that's just speculation.