@greenlight149, I just intend to be helpful on the math problem, without the conflicts I sense shaping up.

Look first at the total force on each cyclist. Let's say straight down for simplicity.

First, force of gravity on him, which is mass * g.
Second and opposing, force of drag, which is the same or more for the heavier rider.

Total force on the cyclist is the former minus the latter. F=Fgravity - Fdrag. His acceleration is total force /mass , or (Fgravity - Fdrag)/m. The m cancels out on the first term so it's just "g", but not so for the second term. So the heavier guy's drag is divided by a bigger mass than the lighter guy, so he accelerates faster.

This is much simplified btw so there's more to it, but loosely speaking the heavier but otherwise identical object falls (accelerating) faster in air.