Mountain Biking - Crank length dilemma

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xfimpg
03-19-10, 09:22 PM
Howdy

If you have 172.5mm cranks on your roadie, should you go for 170 or 175 on your mtb?

I'm thinking 170 to promote easier spinning due to the shorter arm length.

Anyone have any recommendations...?

EDIT: 172.5mm for mtbs tend to be very expensive so i'm staying with standard lengths.

dejock
03-19-10, 09:27 PM
I run 170mm cranks on my 1x8. Ive had no pedal strikes since.
Zephyr11
03-19-10, 10:25 PM
175 is standard. Most riders go a little longer for mountain.

electrik
03-19-10, 10:26 PM
175... there is less spinning off-road and more torque needed, the extra bit of leverage helps.
sscyco
03-19-10, 11:30 PM
175 is standard - last year I switched to 172.5 (after over 10 years with 175) and it was a good thing. Typically I was a masher - took every climb in my middle ring - but figured out that was just taking my knees out and not making me any faster. With the lower leverage and higher cadence I find I am a bit faster. On a DH bike 170 (mine) or even 165 are common - because of clearance and the lack of needed torque. For you I would go with stock and change later - if needed.
stapfam
03-20-10, 05:52 AM
Difference between 170 and 175 is 1/4". If you can tell the difference- you would have to be a Pro that needs the ultimate in bike fit.

Road bikes- 165 for spinning and mountains- 172.5 for flat rides. Still can't tell the difference but the bikes are set up for the different uses. Mountain bikes and 170 on all. Probably because the 170's were on offer without an alternative at the same price.