Crank arm legnth

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Crank arm legnth

Postby bax » June 12th, 2013, 11:32 am

Just curious on some of your thoughts on crank arm legnth/and your height = preference. When I BMX'd back when (way back - walk barlow tomac sheridan) I use to run 180-185 Ashtabula 1 piece cranks, you could go from 165's an up.The 180's suited me well (I'm 5'10) and for the most part you were in an all out sprint, but it allowed for a larger ring gear and for certian tracks worked great.

I'm looking to get a 29'R sometime and thought about tryin some 180's out but wanted to here what you guys have to say. 8)
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Re: Crank arm legnth

Postby drewlee13 » June 12th, 2013, 11:56 am

I ran 180 1x for a long time, enjoyed it. Now I am on 175 since xx1 does not come in 180. I have a shimano xt m770 crankset to sell if you want?
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Re: Crank arm legnth

Postby Laser4G63 » June 12th, 2013, 3:54 pm

I was using 175mm arm length, but since switched to 170mm. I supposed it may have a lot to do with the type of rider you are, whether you mash or spin. I am a spinner and notice I can do so better with the 170s. I know 5mm isn't much, but it's working for me. I am 5'11", btw.
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Re: Crank arm legnth

Postby amadkins » June 12th, 2013, 5:50 pm

Laser4G63 wrote:I was using 175mm arm length, but since switched to 170mm. I supposed it may have a lot to do with the type of rider you are, whether you mash or spin. I am a spinner and notice I can do so better with the 170s. I know 5mm isn't much, but it's working for me. I am 5'11", btw.


This for me as well. I'm long in the torso tho. I found 175s hurt the front of my knees on long rides.
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Re: Crank arm legnth

Postby jiml » June 12th, 2013, 7:49 pm

Hey bax,

I ran 180's back in the day as well, but on the 20/24", you're mostly standing and sprinting from corner to corner. Good leverage for out of the gate and accelerating quickly out of the turns, but I dunno if I'd want to be spinning those long cranks while sitting in the saddle for long stretches when you want to get a good ankle whip going. Just food for thought, as I've pondered this question as well. YMMV.

My guess is the knee pain is the extreme flexion/extension at the top (12/6 o'clock) of the stroke due to the longer cranks, if you don't have the bone length. Again, prolly not too much of a deal while standing but the saddle time is what kills it.

You ran a gear other than 44x16? 8)

Jim

btw, I'm ~5' 10" /* edit - and run 175mm on my 26/29" bikes */
Last edited by jiml on June 12th, 2013, 8:43 pm, edited 1 time in total.
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Re: Crank arm legnth

Postby MediumRB » June 12th, 2013, 8:31 pm

I'm 5'8" with 30" inseam. I spin more than I mash, so narrow tread and 170mm crank arms for me.
Everything I ride makes sense.
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Re: Crank arm legnth

Postby iamkickstand » June 12th, 2013, 8:56 pm

165mm on the DH bike, I think 170 on the xc bike
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Re: Crank arm legnth

Postby b_b » June 13th, 2013, 6:55 am

At 5"10 I think 175 should be a pretty good length for you, but your actual inseam (not pants size) is a better indicator (I wear 32" and my inseam measures 33"). One study found that shorter cranks vs longer (appropriate for you) actually allow you to get up to full power sooner with little downside. I understand the guy who won Mohican overall on a SS uses 170mm cranks. :) Some random info I had bookmarked on this subject take it with a grain of salt...
length study
length info]
length theory/formula
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