Originally Posted by
Leisesturm
What does any of this have to do with bees, dead or alive?? But this is very interesting: "Supposedly, the ideal crank length for maximum production of power, irrespective of the size and conditioning of the rider, is 145 [mm?]". Really? This is astoundingly interesting. Where did you hear this? How do we reconcile this with the reality of 165, 170, 172.2 and 175 cranks on production bikes all over the planet??!! This sounds like an AI fail and I don't really need to remove a crankset to test it. Besides, a drivetrain is more than the cranks alone. The gear set is also important. A 145mm crank is about 20% less in potential torque than a 175mm. You won't even be able to turn the big small and all the rest are going to feel 20% harder to spin. Ideally the new crank would be married to an entirely new chainring set and cassette.
Some racers are apparently finding that short cranks suit them better ergonomically, thanks to a reduction in the required range of knee articulation.
That's one factor. Another is that a bicycle's drive train is a series of levers: the crank arm, the top of the chain ring where it contacts the chain, the top of the sprocket where it contacts the chain, and the radius of the tire where it contacts the ground. A change in the length of any one or more of those levers can be compensated for by a change in the length of one or more of the others.
In the case of the UAE and Visma team members, at least some of whom are using 165-mm or 160-mm cranks or even shorter, they've found that spinning lower gears (longer cog levers) at slightly higher cadences is more ergonomically efficient and more than makes up for the reduced leverage of shorter cranks. As shown by their race results.