Crank length - what difference?

trevorfuller

Hi there,
I've been eyeing up the Race Face Atlas cranks and BB, and have been offered a set for 1/2 price (170mm). However I've not much experience with different crank lengths. I assume it is measured from the centre of the BB axle to the centre of the pedal axle? In which case i'm currently running a with 180mm stolen off of my old hardtail , so they would be shorter than I'm used to.

I keep catching the pedals every now and then since I've moved them onto a full suss frame, so the shorter length cranks would definitly be better for that. But what I don't know what what other differences I should expect from loosing 10mm from my crank length? (power transfer, that kind of thing). I have fairly long legs, and I assume the longer cranks would be better for that?

I'm using the bike for a bit of everything really. Some XC, a bit of light freeride, and a bit of donwhill blasting.

Any help would be much appreciated.

Dangerous Dave

I noticed a difference going from 175 to 170 - on long XC rides my knees would hurt, and I don't have particularly long legs. In effect you'll loose 20mm, which is a fair amount...

4banger

Don't know if I agree with you there Dave. You would loose 20mm from centre of pedal axle to centre of opposite pedal axle, but this isn't really an important measurement.
The important measurement is the lever arm measured when the crank is in the horizontal position from BB centre to pedal axle centre. This gives your effective leverage, which remains 170mm, just a 10mm difference.
With the shorter cranks, you'll get less torque, so just ride in a lower gear and spin quicker. Shorter cranks will allow you to do this more easily, putting the same power out, just in a different way.