Not completely on topic here, but I've not been able to resolve something about weight and downhill speed. The answer/topic has probably been discussed and resolved on this forum, but I've yet to find it. I even asked this of an engineer last week and his answer didn't come close to satisfying me.

Why----why does a heavier rider seem to descend faster than a lighter rider? If there are forces other than gravity coming in to play, what are they? And if gravity is the only force involved, why should weight matter?

I understand friction is involved, but friction could be equal. Also, wind resistance/drag is a biggie, but in theory and in practice, these factors could be equal between heavier and lighter riders, and would probably favor the lighter rider.

Any help you could give me that would lead me to understanding this better?