Anyone experimented with crank lengths?

[Ray Young]

Just wondering if anyone has tried different crank lengths. All the mtb's iv'e bought seem to come with 175mm cranks. With my inside leg the Sheldon Brown says I should use a 165mm crank but that's for road use, off roaders should use slightly longer cranks for added leverage, that means I should be using 170mm. Any comments, thoughts or witicisms?

[Bearbonesnorm]

I've got a few bikes with 170mm arms and a few with 175mm. I'm not sure that I can really tell the difference although now I think about it all my favourite bikes actually have 170mm arms on. I'm 5' 7" with a slightly longer inside leg than someone my height ought to have

[Ray Young]

I'm 5'8" with a too short inside leg, always have take up my jeans :( .

[didnothingfatal]

I use 180mm on my Single Speed, and always have 175mm on geared cranks. Other than leg length, a longer crank will give more torque, whilst a shorter crank will rev up easier, useful when road biking when cadence is higher and more continuous. The same is pretty much true in buulding engines, when I drag raced VW Beetles, I built several high revving small motors on a 69mm crank, which whipped up rpm quickly, The bigger 'stroker' motors would never rev up as quickly but produced way more torque.

So the theory is pretty sound on crank length, but in real life unless you're a pro rider hopped up on EPO, I wouldn't think it would make much difference.

[Ian]

I think it depends too on what sort of cadence you tend to ride at. Longer cranks are more difficult to spin quickly. Shorter cranks offer less leverage if you've got a slow cadence.

I always tended not to mix cranks lengths between bikes (regardless of wheel size), so that my legs/knees/ankles/hips are used to the same rotational action.

[thomthumb]

i use 175 on my mtbs. put 170s on a bike before - what everyone was doing because of pedal strikes - but i hated it, changed for 175s and the bike rode much better.

my ss/ fixed cross bike/ commuter (pompino) runs 170 and they are fine. my geared roadie runs 175s.

make of that what you will. I'm 5'10". for road cranks i'm right on the borderline between 172.5 & 175.

friend of mine built his last bike (xc race bike) with 165s (from 175s) and says it's amazing wishes he did it before, he's about 5'6" ish....

[Ray Young]

Well it was that time when you need to replace cassette and rings so I bought a new 170mm crankset , fitted it and went for a ride. Did I notice any difference? Well if you concentrate on it then yes I noticed it is slightly easier to spin up to speed but apart from that, not really. The bike lost another 0.8lb though as I was running a square taper jobbie up till then.

[bod]

I always thought that crank length was more of a bike fit thing that depended on your femur length so you knee was in the right position. The Knee Over Pedal school of thought has never worked for me though, makes my arthritis play up. 170-175mm cranks on an 18-19" frame is fine for me (5'10", 32" leg when I buy jeans).
If you want more leverage surely you can just change gear? As for cadence I'm a masher so my RPM is lucky to get above 60 so won't affect me there.