Originally Posted by
PeteHski
In practical terms, the actual variables involved here are mass, air resistance and rolling resistance. Of those variables, mass is the most important when comparing riders on similar bikes.
I can confirm, as just about everyone I ride with is considerably heavier. In order to keep up with them downhill, I need to be more aero, more skilled, and more on my pedals out of each turn.
Steady state downhill coasting speed is a simple static force balance. On one side is:
weight * grade
On the other side is:
(rolling resistance * speed) + (drag coefficient * frontal area * 1/2 air density * speed^2)
A heavier rider descends faster because body mass scales more quickly than frontal area.