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Octalink bottom brackets and spacers

Gabe_62Gabe_62 Posts: 5
edited April 2016 in MTB workshop & tech
I have a isis bottom bracket and there is clearly a 2 to 3mm gap on the drive side. I simply replaced the original with same spec one.

Is it okay to use a spacer to take up this gap and torque each side correctly.... And if so, where the heck can I find one?

Thnx for any advice.


  • cooldadcooldad Posts: 32,904
    Octolink or Isis?

    But either way, you shouldn't need spacers. What size is your BB shell and what size BB did you buy, 68mm or 73mm?

    I'm no expert on either, but they are basically a glorified square taper.
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  • GiraffotoGiraffoto Posts: 2,078
    OP: if the 2-3mm gap is between the crank and the BB cup, it'll still be there if you put a BB spacer on the cup (This may not be what you mean, but I can't think of any other sort of spacer you'd use there).

    Make good and sure you've got an MTB octalink rather than a road one - the road one has a different length of splines! The ne sure you have the right length of axle, the splines are clean and the bolts are done to the correct torque.
    cooldad wrote:
    I'm no expert on either, but they are basically a glorified square taper.
    Well, they're glorified to the tune of being round rather than square and splined rather than a smooth taper. But you use roughly the same tool for getting them off.
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  • Gabe_62Gabe_62 Posts: 5
    Thnx for that.

    The gap is on the non drive side, between the edge of the bb cup and the frame. Gaping ! Can't tighten it up anymore. May be bad tolerances... but either way, wondering if it's safe to use a spacer.

    I have a spacer on my other bike, but that's an XT BB70 HT2... and it's meant to be there.
  • trek_dantrek_dan Posts: 1,366
    External Isis drive? Not the type where you space the cups depending on what chainring set up your running?
  • The RookieThe Rookie Posts: 27,747
    If the cup isn't going all the way in, it may be debris in the thread, have had that before, or maybe you have a 73mm BB when you need a 68?
  • jimothy78jimothy78 Posts: 1,407
    Some cartridge BBs are made specifically to accomodate an e-type (BB fit) front mech, and have a raised flange and a 2.5mm gap on the driveside cup to fit over the mech's mounting plate. If you've picked up one of these, and then fitted it without the mech (or a spacer to replace it), it's possible that you've screwed the driveside cup too far into the BB shell, which would then prevent the non-driveside cup from screwing in all the way.

    A pic of the BB would show if this was the case.
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