bike size and crank arm length

samsbike

Out of curiosity, does crank arm length vary with bike size, so shorter crank arm length with smaller bike sizes?

me-109

It should do, though my lad's 14" MTB came with 175mm cranks. Not the best speccing of components for size fitting.

Monty Dog

As a very rough rule, rider height in cm = crank length in mm. Track riders run 165mm for high cadence and stopping pedal strike, whereas many TT and MTB riders will run a slightly longer crank.

carrock

typically 50-52-54cm=170mm cranks

54-56=172.5mm

58 and over=175mm

StillGoing

Depends on your individual leg length. I ride the equivalent of a 51 but use 165mm crank arms.

MichaelW

Should do but rarely does. You sometimes find 160/165mm cranks on small bikes but not always. It is much cheaper to fit medium cranks to every bike. 170-175mm are medium.
Long and short cranks are expensive and rare. Specialities-TA make 155-185mm.

Frame designers don't help when they make the bottom bracket height the same across the whole size range. This makes long cranks vulnerable to pedal strike and very short cranks set too high off the road.

samsbike

I was asking as i was wondering if at 5 11.5 with 31.5in inside leg I should be using a 170/172.5/175mm crank and would I really notice the difference?

MichaelW

You are medium sized and all of your crank choices are medium so it comes down to personal choice and riding style rather than specific fit. It would be different if you were 5'2" or 6'4".

samsbike

MichaelW wrote:

You are medium sized and all of your crank choices are medium so it comes down to personal choice and riding style rather than specific fit. It would be different if you were 5'2" or 6'4".[/quote


Thanks

drlodge

I was told that 172.5 is the standard now a days, at your height I would use 172.5mm.