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  1. #1
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    Is my Crankset tapered?

    Hi All,

    I'm planning to replace my original crankset that came with my Trek800 mountain bike. I found a replacement crank on Nashbar, but it is designed for a tapered bottom bracket.

    I've put a photo of my crank set on the web,

    http://home.comcast.net/~cynergyou/crank.jpg

    Is my crank set the tapered kind? I think it is, but would like to double check. Thanks!

  2. #2
    me have long head tube TallRider's Avatar
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    Yes, any crankset that's from a low-end mtb, or that looks like the one you've pictured (or both) is a square-taper crank with JIS-taper (the standard for Shimano and -compatible cranks). there is a different taper standard, ISO, used by Campy and a few others, but anything with ISO taper will be clearly labeled as such.

  3. #3
    Senior Member Matt Gaunt's Avatar
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    Does it have a square axle that you can see that the non-drive side crank arm attaches to? If so, you have a tapered BB.
    Matt
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  4. #4
    Senior Member
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    Even if the current bottom bracket is a square taper (and it probably is) you may need a replacement if the spindle length is wrong for your new crank. Nashbar's tech service person can tell you what length their crank requires.

  5. #5
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    Hi All,

    Matt - I do see a square-shape axle and I think I have a plain jane tapered BB. I like the Nashbar crank set because it's cheap, has a granny inner chainring (22 tooth) and it has removable chain rings. It only comes in 175mm lenghts, but that's OK with me since I have a large frame bike.

    What Crank tool do you recommend that I purchase to remove the crank from the BB? I looked at my cranks on my existing bike and I can use a metric hex head socket to loosen the crankarm bolt, but I'm not sure what tool to buy to remove the crank arms.

  6. #6
    Problem Child Odyssey's Avatar
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    For how to deal with square taper cranks, see:
    http://www.parktool.com/repair/readhowto.asp?id=103

    For the tool, anything cheap will do unless you're planning on removing a few crankarms a day, i.e. bike shop work. It should look something like this:


    http://www.wiggle.co.uk/images/cyclus%20720063.jpg

    Basically the outer thread screws into the crank once you've removed the retaining hex bolt, then the inner screws into the outer, pushing out at the bottom until the crank is pushed off.

  7. #7
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    Quote Originally Posted by Odyssey
    Basically the outer thread screws into the crank once you've removed the retaining hex bolt, then the inner screws into the outer, pushing out at the bottom until the crank is pushed off.
    Two thoughts.

    1. Better quality square taper bottom brackets hold the crank arms in place with hex head bolts threaded into the end of the spindle, usually having a 14 mm hex. Cheap bottom brackets use a nut and the end of the spindle has a threaded projection.

    2. Once you've remove either the bolt or nut, check to be see if there is a washer inside. If there is be sure to remove it before threading in the crank puller.

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