# Crank Length



## Guest (Nov 24, 2015)

Not sure if anyone has messed with their crank length, but I had some experience doing that. I reduced the cranks on all my bikes to 165mm.

Anyone else here done that?

Cranking Open a Can of Worms | Mountain Biking for Women


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## Asterope (Mar 11, 2014)

I'm thinking about tinkering with crank length - my SO even suggested it to me as I seem to have plateaued when it comes to climbing... I think I'm going to give this a go!!


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## cyclelicious (Oct 7, 2008)

Nice write-up Anne. Glad you found this helpful in many ways


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## jeffscott (May 10, 2006)

This all makes perfect sense to me....a smaller bike, cranks, wheels for smaller people..

I went from 170mm to 175mm 5'-11'' felt way better...knees hurt for two weeks till they got accostomed to the larger range of motion though.

I would like to point out that 165 mm cranks with a 26 inch wheel is equivalent to a 175 mm cranks with a 27.5 inch wheel....that is the same gear ratio...


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## LadyDi (Apr 17, 2005)

Thank you for bringing up this topic. It's true- hardly anyone thinks about crank length! I didn't until I had no choice: Last year I had difficulty regaining flexion after knee replacement surgery. It was rough trying to get back on my favorite bike (my 29er) but repeatedly finding it too painful to ride. Eventually I re-evaluated the cranks. I went from 175 to 170mm. I was already there and comfortable on both my cyclocross and a 26er. I was thrilled to be able to ride my 29er with the shorter cranks. This seemingly minor change in crank length made a huge difference in my pedaling comfort- knees and back. Did you find you had to raise your saddle a corresponding distance after the swap? I wouldn't have been able to do <170mm cranks on the 29er without running out of seatpost on seated climbs (long legs/low standover frame). My knee bends well now, but I will always consider crank length with future bike purchases.


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## AMN_10 (Jan 27, 2014)

I have been running 165mm cranks on my bikes for quite a few years. Currently I have a Rhyme 6Fattie (650b x 3.0"). I've run 165mm on my past bikes - 29er, 650b, and 26" bikes quite a few years ago.

It works great for me, my fit, and bike setup.


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## LadyDi (Apr 17, 2005)

Stripes said:


> ... The biggest problem is you have to do this aftermarket  I wish bike companies would get wise to make the cranks proportional to the build sizes.


I agree 100%! I am 5'7". For what earthly reason should my bike's cranks be the same length as the cranks on my 6'5" son's bike??


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## LadyDi (Apr 17, 2005)

...and some little kids' bikes come stock with cranks nearly as long as their femurs!


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## ladljon (Nov 30, 2011)

Wished I had known this thirty years ago....went from 170mm to 165mm then to 125mm on the road bike and 135mm on the mtb and CX bikes. Road on adjustable cranks for two week before going with shorter cranks. Had the road crank custom made and had a machinist cut down my CX and Mtb cranks to 135mm


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## Lucy Juice (Dec 29, 2010)

Stripes, how does femur length play into this? I have a 775 mm inseam, but my femurs are long compared to the rest of my body. My fitter told me the 170 cranks on my cross bike were perfect. 

I'd say for those playing with crank length, definitely do it in conjunction with a professional fit. I had thought about going down to 165s on my trail bike, but now I'm glad that I didn't.


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## AMN_10 (Jan 27, 2014)

Stripes said:


> I'm glad to hear it works great for you too  The biggest problem is you have to do this aftermarket  I wish bike companies would get wise to make the cranks proportional to the build sizes.


Right!? I wish the component companies would just make 165mm cranks in all of model of cranks. I think Specialized is the only brand to offer size-specific cranks on their women's mountain bikes - including 165mm cranks.


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## ladljon (Nov 30, 2011)

I'm just over 5' and have a 27" inseam. Have raced mtb since 86....Shorter cranks = better breathing and more power....no knees in my lungs. These were cut down from 165mm to 135mm. I have tried from 90mm to 175mm. Loving the 125mm and 135mm.


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## ladljon (Nov 30, 2011)

I thought 145mm were going to be my sweet spot, until I tried every size from 90mm to 170mm....125mm is gold. There are people out there that can cut down cranks, and there people who make short cranks....There is a way....Turn3Racing


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## mtb_Chris68 (May 25, 2004)

Good day ladies. My wife has recently purchased a XS Giant Liv Intrigue 1 and it came equipped with 170mm cranks. Being 5'0" tall and having a 27" inseam, she is now looking to replace them with 165mm or even shorter. I'm 6'1 with a 34" inseam and ride on 170mm cranks... crazy to think that bike companies think we should both be on the same sized cranks, especially companies marketing female specific bikes to shorter ladies!

Anyway, I thought I'd share some info we both came across regarding cranks available in sizes from 155mm-170mm from Canfield Brother. Fairly reasonable at $200US.

Canfield Brothers Cranks - Shortest DH cranks avialble

We are still looking in to fitment on her Giant, but we are impressed with the range below 165mm.


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## TampaDave (Mar 20, 2015)

My wife and I went through some crank swaps when we both got new bikes. Our observations:

- If your knees hurt, try a shorter crank. 
- Crank arm length affects your gearing. Shorter cranks makes it harder to pedal. You compensate by gearing down a bit and spinning faster. This may or may not be optimal for you (see The effects of bicycle crank arm length on oxygen consumption. - PubMed - NCBI for example.) 
- Choice of pedals might play a role, personally I find it harder to spin on platforms.
- If you single speed, I think you want the longest cranks you can stand. It allows you to carry a higher gear. Less likely to spin out on the flats but you have some leverage (ie, easier to pedal) for mashing uphill. 
- SLX cranks are worth a look, especially if you're running a 1x drivetrain. The crankarms themselves, once you lose the rings, are about the same weight as XT but quite a bit less expensive. Easy to find SLX take-offs down to 165mm on ebay. You can sell the rings on Ebay and get a little money back. Not a terrible way to try out some new cranks without digging in too deep.

Wifey and I have the same inseam, 29". I'm a spinner with bad knees. She's a stomper with good knees. I settled on 165 for my geared bike and 170 for my ss. She likes 175's. Hated the shorter cranks. So YMMV.


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## jeffscott (May 10, 2006)

TampaDave said:


> (see The effects of bicycle crank arm length on oxygen consumption. - PubMed - NCBI for example.)
> So YMMV.


Interesting article the testing seems to have left out the training effect...

ie trained cyclist were used...but they did not train equally on each of the pedal lengths...


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## ryetoast (Jan 24, 2016)

Interesting stuff! My cranks currently have three worn-out chainrings riveted onto them so it's time for some major shopping. My 170mm's have never bothered me, but someone told me that making them shorter lets you move your weight around more easily for manuals and stuff--can anyone corroborate? How much do you have to change before you notice any difference?

Also, the wonderful Sheldon Brown Gear Calculator may help if anyone is thinking of shortening or lengthening their cranks and wondering how it will affect what hills they can climb. I'd prefer not to talk about how much time I've spent designing fantasy drivetrains on this thing...


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## jk13 (May 21, 2012)

Thank you for all the info here everyone, and Stripes for the article.
Just came to add that for those with entry level bikes and/or square taper BBs, we found an inexpensive 160mm option for my daughter's small '15 Jynx Sport that came with 170s. The Sr Suntour XCT Jr can be had under $50. They are a pretty light triple, and all three chainrings (and the "bash guard") are bolted on so they should be no problem to swap to 1x or 2x when she's ready. She is much more comfortable now. Even has a better pace. Sugino and Lasco had some options as well in the $100-139 range.

As much as we'd like a more modern crankset/BB combo on the bike, this inexpensive setup worked well so I thought we'd share.
Thanks again!


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