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Why no 178.5 or 180mm mountain bike cranks?

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6/10/2015 2:45 PM

Besides the obvious (less clearance) is anyone making 178.5 or 180mm mountain bike cranks? There are a number of ways to figure out what size cranks to run (formulas using inseam etc) - all of which point to us taller guys running 180mm+ cranks.

Again, I realize we will clap the ground even more than we already do, but I'd like to try it and see if it makes any difference...

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6/10/2015 4:31 PM

Shimano makes 180mm XT and XTR cranks, some other people probably do too. I have tried 180's and they worked great on easy trails, for racing. Not so great when things got wet, steep, loose, rocky, rooty, I went back to 175's for a while and now I'm on 170's. I think crank length theory makes more sense for road riding than for mountain biking.

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6/10/2015 4:39 PM

Colin McCarthy wrote:

Shimano makes 180mm XT and XTR cranks, some other people probably do too. I have tried 180's and they worked great on easy ...more

They just sucked in the gnar cause you were clapping them more or something else?

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6/10/2015 4:50 PM

I've had 180's on a few singlespeeds. You have huge leverage and it fits the mandatory low rpm climbing style ss imposes.

Your feet are awfully far apart when descending, this makes pumping kind of weird, and fahgetttabout descending non-chocolate foot forward.

On full suspension bikes you can easily compress your cranks into the ground, which isn't good...you just have to be careful, some bikes already do this with 170-175mm cranks though.

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6/12/2015 7:21 AM

My thought is we're only talking about 2.5 or 5mm. Which is at most 0.20 of an inch. The consequences of these longer cranks would be akin to lowering my bottom bracket 0.20". Something I know I could get away with.

If it makes more sense "biodynamically" and I get more power out of a corner, its easier on my knees and/or just works better for my body type- I can't help but think it makes sense.

Why a 5'8" guy with a 29" inseam and my 33" inseam are on the same length crank arm is beyond me. Even by conservative estimates I should be on something longer...

I know in my DH days when I attempted to go to 165 or 170mm cranks I was considerably slower....

May give it a go...

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