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  • Uberbike GXP BB confusion
  • submarined
    Member

    I have an Uberbike GXP BB, SRAM s1000 cranks, and a 73mm BB frame (’16 Whyte 901)
    When I install it as per the instructions (1 2.5mm BB spacer on the NDS, 1 5mm axle spacer on the DS) and tighten the cranks, the bearings obviously have way too much preload and barely turn.
    What’s going on? There are definitely no bearing Shields from the old BB on the cranks.
    If I assemble the cranks off the bike, and tighten up, the distance between faces appears to be 100mm.
    However, when I measure the distance from BB face to face it appears to be about 96.6mm. when adding in the 5mm axle spacer, it seems obvious why the bearings are binding.
    The red GXP spacer is installed correctly (from the inside of the NDS bearing)

    Anyone else had similar? I’d prefer to find the source of the issue (I suspect I’ve done something stupid) before just custom shimming it from the spares box..
    I didn’t have this problem with the previous BB (Hope).

    Premier Icon thisisnotaspoon
    Subscriber

    You only use 1x 2.5mm spacer on the drive side with a 73mm shell. Nothing on the non drive side.

    GXP has zero preload on the bearings. The step on the axle clamps the non drive side bearing between the axle and the crank arm to stop sideways movement and the drive side bearing is allowed to float on the axle.

    submarined
    Member

    Yeah, that’s the way I understood it. I only have 1 spacer, and that’s on the NDS.
    The BB however, comes with a 5mm spacer that slips onto the axle before installation:

    View post on imgur.com

    Premier Icon thisisnotaspoon
    Subscriber

    Yep sorry. Thought you meant 5mm of spacers. I think that’s probably there because SRAM BB’s have circlips to keep the bearings in the shell. Other brands don’t so the bearings migrate out of the shell. I 3D printed some spacers in 0.5mm increments to fit mine in the end.

    If you’re sure it’s all assembled correctly and just a bit tight, measure the width of the whole setup with verniers, then take it apart and do it again without the axle spacer. It should be the same? If it is just tight you could carefully sand/file the spacer until it fits without binding.

    Just keep an eye on the drive side bearing, it should sit nicely on the raised and machined section of the axle if it’s all spaced correctly.

    otsdr
    Member

    Try without that 5mm spacer, some gap is acceptable on the DS. If you are worried about water ingress, you can use a suitably sized O-ring instead of the spacer.

    submarined
    Member

    I’m more concerned about the bearing walking as described above tbh. Was considering removing the NDS BB spacer as that should mean a 1mm gap or so on the DS.

    submarined
    Member

    Right, this is really getting on me nawks.
    I’ve removed the spacer on the DS and tightened the cranks -as soon as I get any decent torque in the bolt the bearings start binding.
    The only thing that I can see would cause this would be that either the NDS bearing and ‘top hat’combo is too wide, or the cranks have some sort of machining issue on the taper (there is a slight step, not sure if they all have this?)

    Other than machining down the top hat, I can’t see a resolution to this.
    I’m so frustrated with it I’m thinking of putting a SRAM BB back in. At least then it’s a trouble free replacement every few months.
    Never had this with the original SRAM BB or the Hope one that was in there before (but the Hope one has 2 Top Hats, preventing over tightening of the bearings)

    Premier Icon thisisnotaspoon
    Subscriber

    Is the top hat the right way arround?

    The little step on the axle is where the drive side bearing should rest, it measures 24mm, the rest of the axle is slightly undersized.

    I’ve had reasonable life out of SRAM BB’s, they’re certainly better than the joke they were years ago.

    andyl
    Member

    hmm, no problems here on my Aeris with an Uberbike BB and Sram GX Eagle cranks.

    Can’t remember if I used the 5mm spacer, isnt that for road cranks?

    edit: ahh no, top right image 5mm spacer is correct

    https://www.uberbikecomponents.com/downloads/bbfittingguide.pdf

    have you tried assembling the NDS cup onto the axle off the bike?

    deadkenny
    Member

    At least then it’s a trouble free replacement every few months

    I don’t get what people do with their SRAM GXPs. Mine last a couple of years. Year at worst.

    submarined
    Member

    Top hat definitely fitted the right way round (pushed fully ‘home’ from the inside), yup.
    Cheers for the step info – that’s cool, thought as much.

    I’ve tried assembling off the bike, yeah, and it does exactly the same – meaning is has to be something to do with that setup in the axle, so it has to be the spacer width.
    TBH the bearings are now shot (on both sides) so I need to replace anyways. I may try the GX cranks off my other bike on this BB, and these cranks on the BB in the other bike (Hope) to see where the issue lies.
    In regards to what I ‘did’ to the BB that came on the bike? Rode it. Washed it with a hose once in a while, did about 250 miles tops in all weathers. I’ll get another one ordered for simplicity.

    I had exactly this on my Whyte T130 with a Uber bottom bracket.
    Only way I could fix it was to file the 2.5 spacer down.I removed 0.1 max and then it worked fine.

    submarined
    Member

    Well, FWIW, I’ve just fitted a SRAM GXP BB in the exact same way (but with no axle spacer) and it’s bob on. I reckon the issue is with the GXP spacer on the NDS.
    I guess I can keep the cups, bin the spacer, and shove some new bearings in then use it for a Shimano crank.

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