1. The most important thing about buying a new bike is to make sure it fits. The only way you'll know if the bike is right for you is to size up the bike and make sure that the bike's geometry matches your body's geometry. Ask questions and do some research.
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2. If possible, try to find a shop that will let you demo the bike on real dirt. Five minutes in a parking lot won't cut it. You wouldn't buy a car without a real world test drive, and a bike should be no different.
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Thread: crank length

  1. #1
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    crank length

    Currently I have a Alpha Drive square drive crank 175mm. Thinking of dropping down to a 170 mm crank. Will I gain or lose anything by dropping a size. I have read a article that suggests dropping down for better performance and less knee issues.

  2. #2
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    You'll loose a bit of torque advantage, but if the crank arm length is proper for you, you'll gain a better ergonomic fit, and thus reduce strain upon the body (knees).

  3. #3
    Bicyclochondriac.
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    Quote Originally Posted by imcastock View Post
    Currently I have a Alpha Drive square drive crank 175mm. Thinking of dropping down to a 170 mm crank. Will I gain or lose anything by dropping a size. I have read a article that suggests dropping down for better performance and less knee issues.
    5mm is not that drastic a change. What is your inseam?

    Opinions are all over the map regarding going longer or shorter on cranks. Some of it has to do with you inseam, some has to do with personal preference when it comes to mtb. I found that longer is a little better for standing and mashing, shorter tended to be better for sitting.

    I had to do a LOT of experimentation with different crank-lengths, because I have a 2" discrepancy in my leg length. Tried various combos of 165, 170, and 175 arms. Square taper cranks can be had pretty cheap, so it was easy for me to experiment. Too long a crank on my short leg made me feel like my knee was bent too far at the top of the stroke when sitting.
    15mm is a second-best solution to a problem that was already solved.

  4. #4
    linkwvu
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    Personally, I just dropped down to a 170mm from a 175mm and cannot tell one bit of difference in the length change. I went from a very basic SRAM Powerspline 3 ring to a XT Hollowtech 2 ring (for a 2X10) can tell a big difference in the quality. Much more solid and feels like the power I put down gets transferred to the wheel very efficiently. (FYI: I am 6'1" with roughly a 33" inseam)
    Last edited by LinkWVUin FL; 01-16-2013 at 12:33 PM. Reason: Add Info

  5. #5
    Shorty
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    Went from a 175mm to 165mm. The first thing I noticed - it was a lot easier to get out of the saddle and crank it (no pun intended) up an incline w/o the usual muscle burn from the longer cranks. Second, reduced knee pain. Of course, I am only 5' tall with a 27" inseam.

    There are some interesting articles on the web regarding this subject (ie, Sheldon Brown). You can also find crank length calculators which are fun, too! Good luck to you.

  6. #6
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    I am also trying to get my cadence up also. So a shorter crank will help with that too. I am a runner snd will be doing tri's with this bike.

  7. #7
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    I just went from 175 to 170, mostly because I get a ton of pedal strikes, but also because I'm 5'10" with a 30" inseam. Short legs.

    I honestly don't notice the difference pedaling, but I also haven't hit the pedals as much. I've only got 25-30 miles on the new cranks though. What sucked is that I couldn't test it out before installing on my bike, so it was kind of a crapshoot.

    At the very least, there don't seem to be any negative effects, and I've got nicer, stiffer, lighter cranks now. Shifts better too.

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