BB86 press fit compatiblity?

on-yer-bike
on-yer-bike Posts: 2,974
edited March 2015 in Workshop
Ive just installed a Sram GXP bb86 into a BMC frame and it s creaking like mad. The one I removed was Shimano and was silent. Two questions:
Can Sram red cranks be used with Shimano BB?
Is it possible the frame was built only to take Shimano press fit and that the Sram is a slightly smaller diameter?
Thanks
Pegoretti
Colnago
Cervelo
Campagnolo

Comments

  • Monty Dog
    Monty Dog Posts: 20,614
    You may be able to use a SRAM crank with Shimano BB - requires a top-hat reducer bush on the non-drive side as SRAM crank spindle is stepped.
    BB86 is a standard size so should be compatible between brands. Make sure you haven't damaged the bearings during installation. I have two bikes running BB86/92, a CX and MTB and both remain creak-free.
    Make mine an Italian, with Campagnolo on the side..
  • on-yer-bike
    on-yer-bike Posts: 2,974
    Monty Dog wrote:
    You may be able to use a SRAM crank with Shimano BB - requires a top-hat reducer bush on the non-drive side as SRAM crank spindle is stepped.
    BB86 is a standard size so should be compatible between brands. Make sure you haven't damaged the bearings during installation. I have two bikes running BB86/92, a CX and MTB and both remain creak-free.
    The bearings were pressed on with Park headset press using the two special smaller plates and the bearings felt great after installing and the cranks span freely.
    Pegoretti
    Colnago
    Cervelo
    Campagnolo
  • robbo2011
    robbo2011 Posts: 1,017
    My BB86 BMC frame has a SRAM GXP bottom bracket installed and no creaking at all either from the original one or the one i replaced last year. So I don't think the frame would bedesigned specifically for one or the other.
  • on-yer-bike
    on-yer-bike Posts: 2,974
    robbo2011 wrote:
    My BB86 BMC frame has a SRAM GXP bottom bracket installed and no creaking at all either from the original one or the one i replaced last year. So I don't think the frame would bedesigned specifically for one or the other.
    Is yours an SLR02? I think this is 2014 SLR02 with external cables.
    Pegoretti
    Colnago
    Cervelo
    Campagnolo
  • robbo2011
    robbo2011 Posts: 1,017
    2012 SLR01
  • maddog 2
    maddog 2 Posts: 8,114
    Can Sram red cranks be used with Shimano BB?
    No. But you can get spacers to convert King/Hope BBs to run a GXP crank

    Is it possible the frame was built only to take Shimano press fit and that the Sram is a slightly smaller diameter?
    No. They are the same.

    GXP is more creaky than std. 24mm in my experience. Because there is no lateral preload on GXP, the tolerances need to be spot on. I've since moved away from GXP as I got tired of having to regrease it to avoid creaks.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • on-yer-bike
    on-yer-bike Posts: 2,974
    maddog 2 wrote:
    Can Sram red cranks be used with Shimano BB?
    No. But you can get spacers to convert King/Hope BBs to run a GXP crank

    Is it possible the frame was built only to take Shimano press fit and that the Sram is a slightly smaller diameter?
    No. They are the same.

    GXP is more creaky than std. 24mm in my experience. Because there is no lateral preload on GXP, the tolerances need to be spot on. I've since moved away from GXP as I got tired of having to regrease it to avoid creaks.
    What do you mean by lateral preload? Is it that the little black plastic disc on Shimano NDS? Anyway the noise turned out to be the rear mech hanger which on a BMC wraps round both sides of the drop out. The cups on GXP are supposed to be fitted dry according to instructions. You live and learn
    Pegoretti
    Colnago
    Cervelo
    Campagnolo

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