Showing my ignorance...

tdl123321 said:

Guess it is a dumb question but here goes...

Will a 90 kg rider with a FTP of 3watts per kg be faster or the same speed as a 80 kg rider with a FTP of 3 watts per kg.

I'm guessing the heavier rider is faster on the flats(& downhill) while the lighter rider climbs faster.

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Climbing speed is determined by watts/kg. So the two riders will climb at the same speed (all else being equal).

Flat ground speed is governed by watts/cda (drag). Drag doesn't scale linearly with increase in mass, so it is likely that the larger (but more powerful) rider will be faster, but not necessarily.

Whoawhoa says:

Flat ground speed is governed by watts/cda (drag). Drag doesn't scale linearly with increase in mass.........

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Nice. Seriously whoawhoa, if you REALLY ARE a high school student I hope your school offers Advanced Placement Physics and you are taking it!

what I think about it is that w/kg thing is not the entire determinate of speed while climbing. If you think of it as "will a hypothetical being that weighs 1 kg be as fast on a 1% climb as a cyclist that weighs 100 kg and has the same power to weight ratio" there is no way. In this case, whats true in extreme degree will be true in a lesser degree. but to answere the question, in my opinion, the heavier rider will beat the lighter rider (only if they have the same w/kg) on every hill but a hill that is strait up. It really is stupid to view an "absolute" change in the physics of something such as that. how differant is a .oooo1% grade from flat, but by the reason that you are using, the total power is nullified and the power to weight ratio takes total control as the determinant for speed when you enter any hill, even one unoticable to anyone.