Hey XC Purists: what crank length?

I’m considering installing some longer cranks on my Nimbus 29er and venturing off road. Currently, I have 125mm cranks and I’m considering 170mm or 175mm so I can have lots of leverage. I’m also thinking that the super long cranks will lower my center of gravity on such a large wheel (lower my seat another 2”-3”), thus giving me more stability and the sensation of sitting into the wheel as opposed to being perched up high. Don’t know if my logic is right since I haven’t tried it. What do you think? I notice a lot 29”XCer’s use smaller 150mm cranks, however, my terrain (Durango CO) is very hilly. Thanks in advance for any advice.

I have 160s on mine, and consider them a good compromise. For me 170s are for Cokers. But then it really depends on your local terrain. I don’t ride my 29" on the really technical stuff. But then again my Wilder now has 145s on it, and so far I’m pretty happy with those over the old 170s.

I would say go with 150s for xc. I used to use 165s (because they came with the unicycle) and liked them, but I changed to 150s a couple of years ago for an experiment and never went back. 125s are probably a bit too short unless you’ve got VERY strong legs or you’re riding smooth flat routes - from what you said about hills I would stick with 150s. Down hill is where I feel the most disadvantage of 150s over 165s - there’s a longish hill on my commuting route that varies between 1:7 and 1:5 for nearly half a mile - I can climb it on 150s pretty much as easily as on the 165s, but going down really makes my legs burn (and I do claim to have quite strong legs). You could use short cranks and a brake, but it’s just something else to go wrong and clog up with mud.

BTW, I normally ride a 26x3" unicycle - very nearly the same diameter as a 29er (less than an inch in it if you put them side by side), but a bit heavier.


EDIT: Oh, and another good thing about shorter cranks for xc is less chance of pedal strikes on singletrack :slight_smile:
I wouldn’t worry about the c of g thing - I doubt it makes any noticeable difference in practice.

What Rob said. Long cranks help on down hills more than anything else. They may slow you down an increase the risk of pedal strikes. They will make mounting a little bit easier. They will make steering a bit clumsier. 150s would be a sensible compromise.

Or you could get a 700c x 23 mm tyre, skinny lightweight wheel, 114mm cranks and run up the hills with it over your shoulder.

haha get a 20", then get some 175s for it!
that would be awesome!!!

tbh the higher up you are the better the balance. If you have brakes and have steep hills don’t go over 150’s i say

I use 125s on my 29er, but that’s because I ride it more on-road than off-road. It still works when I ride it off-road, but I’d say 140-150mm would be better for hilly terrain. I would not consider cranks longer than 150mm for a 29er, no matter what the use; cranks that long really lose the value of the 29er, and you’d be better off with a 24" MUni with shorter cranks.

For XC Kris Holm recomends 29", 150 cranks plus a brake for downhills

what’s with you and 175’s on a 20 lately?

Thanks everyone for the advice. 150mm’s it is. If I find a good price on them, I might even get some 160mm’s as well. Thanks again. Kevin

If you have a KH isis hub i have some brand new 150mm that i will sell. They are brand new and i only rode on them until i noticed they were 150mm instead of 175mm. PM me if anybodys interested.

You’re in Colorado? 175s. :wink:

Timbob - I have a square taper hub. If any has any used square tapered cranks arms in a variety of sizes, I’d be interested in buying them. Please send me a private pm. Being new to Unicycling, it would be nice to try a variety of different size crank arms to see what works for me and before going all out and buying a nice crankset. Seems like there would be a market for an affordable adjustable crank. I’ve seen those kooka’s and others, but they are extremely expensive. Thanks.

29er cranks


I would go with 150s. If you are riding back in Horse Gulch, that will work well for the places you can ride–things like the Anasazi Descent are out of the question for sane people. One of the nicest rides I have found there is the Sidewinder Trail or the Big Canyon Trail, I use my KH29XC with 150s.


Cotterless cranks are cheep, $12-$25. So if nobody already has a set, you can buy a set of four at UDC for under $70.

i don’t know
it just feels cool