CRANK ARM LENGTH

[openmind]

Yes, down to 170 from 175.

If you did not change your saddle height also then I would bet on it that your saddle sore disappeared not because of the shorter crank but the unintended effect that your saddle-to-pedal distance was reduced by 5mm. You effectively lowered your saddle by 5mm which often solves saddle sore problems (because it tends to make you sit more on your sit bones).

[Eugene]

I've ridden the same frame with 170mm, 172.5mm and 175mm and must say that I cannot feel the difference at all.

[Capricorn]

If you did not change your saddle height also then I would bet on it that your saddle sore disappeared not because of the shorter crank but the unintended effect that your saddle-to-pedal distance was reduced by 5mm. You effectively lowered your saddle by 5mm which often solves saddle sore problems (because it tends to make you sit more on your sit bones).

 

you will always sit on your sit bones (unless your saddle is too narrow, but that's not a factor in this case), but the shorter crank arm will reduce the amount of rotation of the femur at the hip as the knee doesn't have to go up as high with the cranks at 12 o clock. Less relative thigh movement, less range of rubbing. Its that thinking that i based my wild guess on.

[intern]

As a matter of interest, I recently bought a bike which has 167.5mm cranks on it; I've always ridden 172.5mm (apart from the late 1980s to around 1993 when 170mm was standard).

 

I could immediately feel the difference in shorter cranks - it felt a bit odd at first, but you know how it is, within 4 rides it's normal.

 

Now, I've ordered and paid for a fancy Praxis BB to convert the Specialized OSBB to a standard SRAM GXP so I can whack some 172.5mm Red cranks on the bike...but I don't think I will bother. Having gotten used to the shorter crank, and favouring a higher cadence (usually average 91-92 on the road and 100+ on the rollers), I do believe the slightly shorter than usual ones may actually play to my advantage.

 

At the very least, I don't feel like I am any slower or less powerful on account of the short cranks - and this way I can retain the pretty snazzy Specialized carbon crankset (though the Red ones are pretty, too.)

[FrankieKnuckles]

Apologies of this has been beaten to death before:

 

What are the implications of shortening your crank arm length, say from 175 mm down to 172.5 or even 170 mm? If you calculate the % difference in the circumference described by one revolution, it's negligible.

 

Surely you can achieve the same thing by staying with a 175 mm crank arm, and changing chainrings: going from a 40 tooth, down to a 38 tooth in the case of MTB?

 

Or is there a whole bunch of physics and physiology I'm missing here - power transmission, torque, effect on endurance, etc?

Not sure if this has been posted :

 

http://www.cyclingweekly.co.uk/news/latest-news/are-shorter-cranks-better-188288?utm_source=Facebook&utm_medium=Social

 

Worth a read.

[tombeej]

Yes, without a doubt, shorter is better. For all riders - tall and short. All the research is saying so. The old thing of 'longer cranks for tall riders, short cranks for short riders' has been thoroughly debunked. I'm 6'2" and I went down to 170mm. A noticeable improvement for me, esp. in terms of reduced fatigue over long rides/races. But have no doubt it would be even better if I went to 167.5mm.

[intern]

Interesting comments guys. Look, I think crank length is one of those things for which you can find any amount of evidence to support whichever viewpoint you have. However, the bottom line is probably that you might as well be happy with what is on your bike, regardless of whether it got there by accident or design - because in the greater scheme of things, it probably makes little difference either way.

Which means I'll leave the S-Works cranks on just because they look cool  .