Originally Posted by
Salubrious
I am not assuming a significant peak, and I suspect that there is a macho thing that says to use a larger crank. I am also assuming that there is a peak, that is all. Every person has an ideal fit of a bicycle for their physique. We have different seat heights and angles, different stem lengths, different frame sizes, yet somehow in all this all people can all use the same size crank?? That does not follow logically.
If you look at the crank, foot, and leg, there is lever action in each part. The most significant part of the lever mechanism is your leg, not the crank. For this reason the crank has less effect than your leg does, but to discount it entirely would be a mistake. I covered this already in a prior post.
The study only shows that with the lengths used, there is not much difference. It simply does not have the resolution to show that there isn't a peak in performance with a particular length- that would be an unscientific conclusion. It certainly does not disprove the French formula. I suspect that the people who did the study were not even aware that the French *had* a formula.
I agree that the improvement in rider performance is not going to be much, but why leave that on the table?
Well, we are unlikely to agree. Nevertheless, I find the topic interesting and am a bit frustrated at the relative dearth of actual study of the subject where a variety of riders were investigated along with measurements of power output and efficiency. What is up there on the Internet is largely opinion, recitation of formulas that seem to have been calculated from inseam measurements and such without actual science behind them, and case studies of individual riders, again without comparative power output measurements against other riders and the like.The Martin study I linked to seems to be accepted as the current state of the art in terms of a replicated and scientific investigation.
Here's another study with recumbants that shows no significant difference in efficiency with crank length:
http://www2.gcc.edu/dept/math/jackso...-%20poster.pdf
Sram offers some opinion around crank lengths and references the Martin study I previously linked to. They opine that we are using cranks that are too long, at least for some types of riding.
http://www.theroaddiaries.com/2013/0...-with-options/
They also state that shorter cranks are less efficient at slower cadences such as for hill climbing. What may be going on here is that at shorter crank lengths, the cadence can increase, although with less torque, and at longer cranks lengths you will have a lower cadence but with increased torque. So efficiency tends to level out over crank length as the rider compensates. Somewhere in there a rider will find the crank length that gives them a cadence and torque combination that feels best to them, and possibly will give them their peak output. Apparently, however, we can adapt over quite a range of crank length, although a specific crank length may feel best to us for a variety of reasons.