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  1. #1
    MTBR member-at-large
    Reputation: ThornPatch's Avatar
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    Jan 2004
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    Smile Help with gear slippage

    For all the mechanics and drivetrain experts out there I have a question for you.

    I have a KHS Team XC (4" full suspension with Specialized's FSR rear end) with a custom build and I'm have a terrible gear slipping problem.

    The problem only occurs when I'm in the granny gear up front, and either of the two largest cogs in the rear (I have a 11-32 cassette) and only when I'm climbing really steep trails (hence more torque on the drivetrain). the bike shifts fine while in the workstand, or riding on the flats.

    Here's the list of drivetrain parts:

    -RaceFace Next X-type cranks 22-32-42 (new)
    -Sram PC991 chain (new)
    -Sram PG 990 11-32 cassette (new)
    -Sram X-9 medium cage rear derrailleur (older, but in good condition)
    -WTB LaserDisc Lite rear hub (new)

    I don't trust my local shop to look at (they screwed up my road bike the last time I brought it in) so any help you can give is very much appreciated.

    Thanks in advance!
    Better at pedaling than typing

  2. #2
    monster member
    Reputation: Wheelspeed's Avatar
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    Have you tried turning the cable adjuster while riding? It's very typical to get everything right while spinning on the stand, and then have to fine-tune it while riding.

    First step is to figure out which way it's "slipping". Trying to shift to the next smaller cog?

    If so, turn the cable-adjuster CCW.

    You can also visit the Park Tools website's help section. They have a very good section on adjusting derailleurs.

  3. #3
    mtbr member
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    Patronising question this, but did you physically measure the bottom bracket shell width and apply the appropriate spacers and/or elastomer preload rings to shim out the external bearing cups so that the cranks can be tightened firmly against the cup seal surface?

    Whack the drive-side crank at the bottom bracket centre with the palm of your hand to see if there is any movement inwards towards the frame.

    Another cause is a loose freehub body which can rock and make the chain slip. Remove the cassette and check the freehub body by rocking it back and forth. Approx 1.5mm of movement is acceptable, but any more means that you will need to unscrew the freehub and fit a new 1mm thick washer to take up the rocking movement.

    Btw, also check that the axle is bolted tight (but spins freely) against the wheel bearings - cone spanners are good for this job.

  4. #4
    mtbr member
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    Another common problem on dual suspension bikes is cable housing that's too short. It'll work just fine in the stand but when you're riding the bike and the suspension is cycling, it'll pull on the derailleurs causing skipping.

  5. #5
    MTBR member-at-large
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    Thanks for the advise.

    I think I'll completely disassemble the drivetrain this weekend and start from scratch. I'm going to make sure I didn't miss a spacer, or cut the housing too short.

    I appreciate all your help!
    Better at pedaling than typing

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