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XTR Crankset fitment problem

muddi_camelmuddi_camel Posts: 67
edited August 2013 in MTB workshop & tech
Got a weird (to me anway) problem.
Trying to fit a FC-M970 crankset to my mates MTB frame. It appears as though the crank axle is too long....
It's a 68mm shell, using a third party BB (that appears the same dimensions as most of this style).
I've had to fit in as many spacers as I can lay my hands on, & still can't get rid of the endfloat without the adjuster coming off the non-drive crank.
To keep the chainline right, I don't want any spacers on the drive side really, and any more than two spacers leaves insufficient thread in the BB to engage in the frame properly.
I'm not aware of an XTR specific BB having significantly different dimensions (2-3 spacers worth), so I'm scratching my head on this a bit. I feel I'm missing something obvious......
- Any thoughts?

thanks

Posts

  • Chunkers1980Chunkers1980 Posts: 8,035
    So how many spacers have you used? Have you followed the instructions in the tech doc?
  • njee20njee20 Posts: 9,613
    You need 2 spacers on the drive side (unless he's using an e-type mech) and one on the NDS.

    If you really want you could move them to the other side, but then the cranks won't sit centrally in the frame. If the chain line is that far off then something is wrong with the frame.

    You say you've fitted as many spacers as you can "lay your hands on", but have none on the DS and only 2 on the NDS. Make sure you double check any safety critical stuff before you give it back to your mate!
  • The RookieThe Rookie Posts: 27,810
    muddi camel wrote:
    Got a weird (to me anway) problem.
    still can't get rid of the endfloat without the adjuster coming off the non-drive crank.
    Eh, as you unscrew it to come off you loose preload, try screwing it in!
    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.
  • delete_my_accountdelete_my_account Posts: 192
    Eh, as you unscrew it to come off you loose preload, try screwing it in!

    M970 cranks are preloaded with a nut type thing on the inside of the non drive side arm, such that unscrewng it makes it closer to the BB. Unlike XT or SLX where unscrewing would move it outwards, away from the BB.

    A 68mm BB shell needs two spacers on the right, and one on the left.
    Delete my censored account.
  • muddi_camelmuddi_camel Posts: 67
    It's currently fitted with 4 and a very slim (almost a shim) spacers.
    I can't see the frame being out of line - but I guess it doesn't take much....
    I'll check alignment as best as I can in the morning.
  • njee20njee20 Posts: 9,613
    Are they the correct spacers, or some that were lying around? They should be 2.5mm.
  • Chunkers1980Chunkers1980 Posts: 8,035
    Shimano have started knocking out 2mm and 0.5mm as separate spacers recently.
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