MTB vs Road Cranks Lengths

[Patchelicious]

I have ridden for 2 years on the road now with a 172.5mm crank (This is the correct length I need as confirmed by ErgoFit and Richard at CycleFit.), and have just started doing some MTB too, but realised that my crank on the MTB is 175mm.

 

Now, some people have said its a good thing to have extra leverage on the MTB and others have said keep it the same all round.

 

Opinions?

Edited January 16, 2014 by ArchedBackChinOut

[4u2nv]

i might be mistaken, but i do not think you get a 172.5mm on a mtb, only 170mm

 

someone can confirm

[CASSIE1975]

I also have 172.5mm on ROAD and 175mm on MTB.

 

I spoke to a friend a while back in connection with different crank lengths...he said it's better to have a longer crank (175mm) for the hills (more power and leverage with a bigger diameter pedal stroke??)...therefor maybe the longer crank length on a MTB?? Maybe more power into the pedal stroke for the MTB's??

 

I am not a foondie on the Mathematical Scientifics of the statement he made...

 

Maybe someone can confirm...or "crank" this statement into the ground...LOL

[BenDL]

I think this has been covered before but 2,5mm difference is really nothing, like: | |

 

I doubt you will notice any difference, especially if you compensated for the 2,5mm on your seat hight.

 

I would think that a bike fit would be hard pressed to recommend 172,5mm above 175mm cranks. There are so many variables in measuring body angles, etc. that such a small difference will not make any diffenece.

 

But that's just my 2,5c worth

[Mr X]

I always used 172.5mm with a road bike and 175mm with a mtb. I am going to start only using 170mm on my mtb. I believe most small/medium sized people are using 175mm cranks which are too long for them. The drawback of a too long crank is knee problems and a less efficient pedal stroke. I think that 175mm was just chosen as a standard crank length for mtb back in the day. I believe crank length should be used according to leg inseam length and is the same for road and mtb. It seems that manufacturers are waking up to this and small Giants are now fitted with 170mm cranks. They will do well to fit 170mm to the mediums also, like Bergamont did for 2014.

[grumpy]

i might be mistaken, but i do not think you get a 172.5mm on a mtb, only 170mm

 

someone can confirm

My wife is riding on a 172.5mm XTR crank, it is certainly available.

Both our road and MTB have the same crank length, prefer keeping them the same.

[quintonb]

Generally on the road you ride at a more consistent pedal cadence and more often a higher cadence.

A shorter crank arm allows for a higher/smoother pedal action (less circumference to travel around, the shorter the crank arm)

Track riders tend to use 165-170mm cranks, thats good for a fixed geared bike, helps with a nice smooth high cadence when things heat up.

On a mountain bike you often ride at lower cadence's and have tough (walking pace climbs), here you need the leverage of a longer crank arm where high cadence does not come into play.

 

Hope that all makes sense...