Crank axle lengths

bobbydigital
bobbydigital Posts: 254
edited August 2018 in MTB workshop & tech
68/73mm shell, which size axle is needed? Not bottom bracket but crank.

I'm trying to buy a crank for a short person, me, 165mm crank arms.
Sellers do not know what shell they fit or what bike they are from so they have measured the axles they are between 130 and 135mm long.

I'm guessing that is 68/73 rather than boost. Can you even get a boost crank in a 24mm diameter?

Comments

  • cooldad
    cooldad Posts: 32,599
    BB axle size depends on the cranks. Check out the tech docs for yours.
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  • The Rookie
    The Rookie Posts: 27,812
    Unless it’s a through axle crank, the crank doesn’t have an axle that’s in the bottom bracket, if they are then the axle length isn’t adjustable.

    How about you give us a clue and tell us what cranks?

    You seem thoroughly confused, boost cranks may be no different to non boost (my X0 for example can be used in a 68, a 73, some pressfit and boost or non boost).
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • bobbydigital
    bobbydigital Posts: 254
    Race Face Chester and Shimano Saint M815 and M805,

    I thought boost crank was wider for 83mm shell but I also thought they came in 30mm diameter spec and not 24mm.
  • The Rookie
    The Rookie Posts: 27,812
    Some do, some don’t. And no, axle diameter is dependant on the BB shell and BB fitted in the frame not the rear axle size.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • swod1
    swod1 Posts: 1,639
    Bobbydigital wrote:
    Race Face Chester and Shimano Saint M815 and M805,

    I thought boost crank was wider for 83mm shell but I also thought they came in 30mm diameter spec and not 24mm.

    boost is just the offset of the chainring for 148mm rear hub you can still get them for 68/73mm bottom bracket widths but i guess newer bikes are more 73mm, 68mm i think is more road bike size.

    135mm sounds about right as if you have 73mm width bottom bracket and then the cups will be what 10mm each side, then you have the left non drive side crank arm what 25mm etc.

    Just make sure you buy the correct size for your bottom bracket, as already mentioned there is 24mm shimano or 30mm axle diameters.
  • bobbydigital
    bobbydigital Posts: 254
    Good good, something else learnt, thank you!

    Yeah I'm running bb70 so needs to be 24mm axle.

    Hopefully with get either of them, I have used a chester before, looks nice and performs well, saint might be a bit heavy for xc bike but limited for 165mm cranks in the used market. There are zee cranks but I like to build somewhat pretty bikes and the zee stuff looks like sram nx, a bit boring looking, boring shapes.
  • The Rookie
    The Rookie Posts: 27,812
    Or use a GXP crank and adaptor?

    There are some GX on the evil bay right now and sometimes X0 come up.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.

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