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  1. #1
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    Jumping out of gear - Advice sought

    SRAM X5 rear derailleur
    SRAM chain (brand new)
    Fox Brain Shock

    Have an issue whereby whenever the shock has reason to compress (bump, bounce, jumping on pedals, etc.) the rear derailleur will temporarily pull the chain into another gear. When the shock relaxes, the cable tension pulls the chain back into the original gear.
    Highly annoying, and makes the setup almost useless for XC.

    Thought it might be chain length, but I put a new one on and measured using the big-to-big + 2 links method.

    Does anyone think this might be a hanger alignment issue?
    Or could my chain still be too short for the compressing rear shock?

    Thanks,

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    '04 Specialized S-Works Epic FSR
    '06 Mongoose Amasa Comp hardtail

  2. #2
    Vaginatarian
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    I would check your cable length & routing. unhook the rear shock and cycle the suspension, you should be able to recreate the problem

  3. #3
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    I had a problem like you are describing on my Stumpjumper, and it was a bent dérailleur hanger. It took a shop owner who is detail oriented to find it, because the 1st mechanic I spoke with couldn't induce the problem with the bike on a work stand, and didn't check the hanger. But put the drive train under load and presto, it would skip and catch.

  4. #4
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    Quote Originally Posted by dan0
    I would check your cable length & routing. unhook the rear shock and cycle the suspension, you should be able to recreate the problem
    I'm with Dan on this one. My old Specialized Enduro routed the derailleur cable under the bottom bracket. If that section of housing was too short, it would be pulled slightly out of the cable stops upon suspension compression thus causing a momentary shift of the rear derailleur. Lengthening that section of housing fixed the problem.

  5. #5
    ...idios...
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    You've just fitted a new chain? How many miles are on the cassette?
    .
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    What luck for rulers, that men do not think - Adolf Hitler

  6. #6
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    Thanks all.

    Guess I'll check the cable routing first, then move on to the hanger.

    It's a PIA to cycle a Brain shock "offline" so I'll disconnect it and see what I can see.

    BTW, I have about 500 miles on the cassette, and keep it well maintained.

    Full.
    '04 Specialized S-Works Epic FSR
    '06 Mongoose Amasa Comp hardtail

  7. #7
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    Quote Originally Posted by KevinB
    I'm with Dan on this one. My old Specialized Enduro routed the derailleur cable under the bottom bracket. If that section of housing was too short, it would be pulled slightly out of the cable stops upon suspension compression thus causing a momentary shift of the rear derailleur. Lengthening that section of housing fixed the problem.
    This sounds real plausible to me as well.

    As an aside, checking the hanger took less than 5 minutes. You just flip the bike upside down, attach the tool and check the alignment.

  8. #8
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    Resurrecting this old thread to close it out with a report...

    ...It was indeed the cable routing under the bottom bracket, exactly as described by KevinB.

    I replaced the cable, giving the new one some additional length under the BB, and the problem has gone away. You live and learn!

    Full.
    '04 Specialized S-Works Epic FSR
    '06 Mongoose Amasa Comp hardtail

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