Originally Posted by ShannonM

There's a meme (in the original sense of the word, a unit of cultural heredity, not the modern stupid-picture-of-a-cat-with-a-stupid-saying-in-white-letters sense,) that has been replicating in the brains of humans who ride bicycles for many, many years... and it's nonsense.

That meme is this:

Flex in the bicycle dissipates some fraction of the force generated by the rider's muscles.

This is simply, physically, not true. The thing that it's describing does not actually happen. Numerous attempts have been made to measure this "power loss." So far as I'm aware, nobody has ever been able to repeatably detect any power loss due to bicycle flex that is above the noise floor of the equipment used to do the measuring.

And, because the meme isn't actually true, this statement is true:

Unless the bicycle and/or its components are so flexible as to have negative effects on handling, alignment, or durability, the stiffness of any part of the bicycle or the bicycle as a whole is utterly irrelevant to the performance of the bicycle.

Stop caring about the stiffness of your frame, cranks, wheels, stem, handlebar, pedals, brake levers, (yes, I've seen stiffness referred to in brake lever reviews,) or any other part of your bicycle with the possible exception of racks. (And even they're not much of an exception... any rack strong enough for the load you're putting on it will be stiff enough for that load... if it wasn't, it'd break.)

Stiffness does not matter.

--Shannon