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  1. #1
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    Need to know what size allen wrench to use to get crank arms off

    my bottom bracket "unspun" and i need to get them off to fix it. i had an allen wrench that fit but i seemed to have lost it. so i wanna go pick up a new one without having to buy a whole new set. the cranks are single speed FSA's and it's bigger than 6mm if that helps

  2. #2
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    8mm

  3. #3
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    +1 -- It's 8mm, but if an 8mm key isn't readilly available a 5/16" (7.94mm) will do in a pinch.
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  4. #4
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    Mine is 10mm

  5. #5
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    I'd strongly recommend an Allen socket to use with a torque wrench. Getting cranks up to specified torque is pretty critical from what I've heard (though I've always brought the torque up to spec and never had a problem, so I haven't ever seen insufficient torque kill a crank).

    Here's a good unit, assuming that your cranks use 8mm and you have a 3/8" torque wrench (like the bigger Park Tool wrench):

    http://www.mcmaster.com/#8367a45/=2aser4

    To get the cranks off, you need a crank puller:

    http://www.lickbike.com/productpage....=%272430-00%27

    Best of luck.

  6. #6
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    Quote Originally Posted by Lawrence08648 View Post
    Mine is 10mm
    Is it an FSA? All of the Shimano cranks I've ever seen are 8 mm but I came across one requiring a 10 mm and, IIRC, it was an FSA.

  7. #7
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    Perhaps you can just measure across the hex opening?

  8. #8
    Great State of Varmint Panthers007's Avatar
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    Park Tool makes a nifty tool that they say will take off the bolt on cranks. It is 8mm. Since I bought that tool - I haven't seen a single 8mm bolt on a crankset. Only 10mm. I suggest getting a full set of metric allen-wrenches. I even have a 7mm - though I've never used it!* LOL!


    * - inside joke for mechanics
    How do you keep an idiot in suspense?

  9. #9
    Insane Bicycle Mechanic Jeff Wills's Avatar
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    Quote Originally Posted by Panthers007 View Post
    I even have a 7mm - though I've never used it!* LOL!

    * - inside joke for mechanics
    Ever had to work on the early-90's Campy self-extracting cranks*? That's where the 7mm comes in handy.



    * - well, neither have I.
    Jeff Wills

    All my bikes.

  10. #10
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    Word.*

    * - I didn't actually buy the 8mm socket individually, I saved myself the aggravation and bought a full set!

  11. #11
    I don't even own a cat... invwnut's Avatar
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    My SRAM cranks use an 8mm. I recommend an 8mm socket allen head. But if you don't want to do that an small pipe or hollowed out lever will help you with an allen key.
    2008 LG Sonix 6.4, 2002 KHS Flite 500, 1999 Big Sur Gary Fisher

  12. #12
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    I initially said mine was 10mm. I just changed my crank and bottom bracket this weekend (with the cassette and chain) and I was wrong, it's not 10mm, it's 8mm. It's a Truvativ, both, the old and new.

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