Crank length

[ethan5]

Hi,
I've got 52/42 chainrings with 11/28 on the back and 170mm cranks; I want to replace them but would it be a good idea, and would I get much mechanical advantage increase, if I replaced the cranks with, say, 180mm ones. I'm coming round to getting 52/39t rings, Durals instead of getting bigger rings, it's a hard pedal on 52/11. I was once passed by a bloke on a mountain bike and that got to me; he didn't look like he was Chris Hoy! Thank you for your time, your comments are gratefully received.

 

[HLaB]

Hi,
I've got 52/42 chainrings with 11/28 on the back and 170mm cranks; I want to replace them but would it be a good idea, and would I get much mechanical advantage increase, if I replaced the cranks with, say, 180mm ones. I'm coming round to getting 52/39t rings, Durals instead of getting bigger rings, it's a hard pedal on 52/11. I was once passed by a bloke on a mountain bike and that got to me; he didn't look like he was Chris Hoy! Thank you for your time, your comments are gratefully received.

The first place I'd look for advice is the late Sheldon's site

I've not read it in detail but he seems to be saying longer cranks may offer a mechanical advantage if you cant change gear right but they are also more likely to give you sore knees.

 

[tyred]

I think the traditional rule of thumb is that long cranks suit people with long legs. Personally, I think they would suit anyone with a slower pedalling style. My Rudge, like all proper roadsters, has 7 1/2" cranks and they do tend to lend themselves to plodding along in a high gear. It's surprisingly relaxing when you get used to it, and you never seem to end up soaked in sweat.

 

[briank]

NOT a good idea to adjust your gearing by altering your crank length. Change your cassette and/or rings if you want to do that. Your leg length and pedalling style should define your crank length. If you do decide to go for longer cranks. I think increasing them by a full 10mm in one go risks damaging joints or tendons.