Originally Posted by
PeteHski
It’s hard to argue with that. But is it a significant loss?
You could attempt to measure the loss across stiff vs less stiff frames using pedal power meters and a rear hub power meter, swapping those specific power meters between the bikes. The bikes would need to have the same drivetrain in the same condition, same chain lube etc. If you could consistently measure a higher differential between pedal and hub power on less stiff frames then we would have something to discuss here. But I have not seen any attempt to measure power loss due to frame flex objectively.
On a more pragmatic level I’m pretty sure none of the bikes I would personally consider riding competitively would exhibit a significant difference in frame stiffness in terms of power transfer. The only thing I would be likely to notice in terms of stiffness is their vertical compliance and thus their ability to absorb road vibration.
It has been done in the recumbent world.
Besides me, there was another recumbent rider on this thread. Lateral flex is not a fast climber in our world. The frames are much longer and the effect is quite exaggerated
The lateral movement of the BB on a flexible frame puts force onto the tires increasing hysteresis losses.
Undoubtedly, some of the stored energy in the deflected frame is returned to the chain. However, if this causes articulation of the chain on the drive side of the chain (top), the frictional losses increase in the chain.