Originally Posted by
Carbonfiberboy
And it may not just be fit. I've ridden "nice" bikes on which I simply could not seem to get the power to the asphalt and others where the bike would keep going faster as long as I kept shifting up. Some mystery of frame design or frame/wheel/tire matchup. I really have no idea other than to test ride bikes.
This is where the hypothesis (i.e. suggested phenomenon) of planing could be posed as an explanation. The idea is, what could be different between two bikes with identical geometry, setup and contact point locations? One answer is that the frame in one bike is transferring energy to the road better than the other one, enabling better speed and responsiveness in a wide range of riding conditions. This has been discussed widely on other sites. The theory is that thinner-gauge frame tubes flex a little more under pedaling stresses (the downstrokes) and spring back at the two bottom positions. When the frame releases its energy the BB shell rotates in the horizontal plane so the crankset is pulled forward, with the result of applying tension in the chain. This of course would add to the propulsion energy applied to the ground, if this suggested explanation is right (planing is not my idea, but the above is my idea of how it could work).
In Bicycle Quarterly there have been articles over the past five or so years documenting riding results that support that planing exists and that it most likely works as above, but I haven't seen really detailed testing at the level of a frame.
Sorry for the long detour, but I'm trying to suggest a performance improvement that is independent from fit, as Carbonfiberboy suggests. I suppose I should start another thread if there's much discussion of this point here.