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  1. #1
    mtbr member
    Reputation: string's Avatar
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    XO chain gap ???

    Lately I have had a slipping sound/feel in my drivetrain. Performance has yet to be affected, but I can hear/feel it. The bikes a Foes FXR with an XO RD, XT FD, XT cassette, and SRAM PC-99 chain.

    I've replaced the chain, cassette, and chain rings but the problem still persits. I have also checked my hanger to make sure its straight.

    I noticed SRAM indicates the chain gap should be 6mm in pretty much all possitions. I can set it to 6mm in the largest gear but when I shift to the smallest cog the gap is closer to 12-15mm. No matter how I set the B-screw tension, the chain gap is never consistent accross the cassette.

    I am wondering if this is a function of the frame/cassette design or if there is a problem with my derailuer. Nothing appears to be bent on the XO, however it is almost 2 years old.

    Some pics are below: 1 in the largest cog and one in the smallest cog.

    Any suggestions?
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    Last edited by string; 11-12-2005 at 04:29 PM.

  2. #2
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    Chain gap has no effect on a skipping chain (if that is your problem- I don't know what a slipping sound/feel means otherwise.) Maybe the freewheel mechanism is going bad. That would make it seem like the drivetrain is slipping.

  3. #3
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    Possibly the derailuer

    I had a similar issue with an older 9.0 rear derailuer (also on an FXR). My problem turned out to be that the derailuer tension spring (the coiled one inside where the cage and body join) had worn to the point that it wasn't keeping proper tension on the chain. Under hard peddaling efforts this would allow the chain to slip. The bike shifted fine on the work stand but not once riding. If you have any other derailuer you can put on that would be the easiest way to confirm or eliminate the X.0.

    Since you have replaced everything else it seems like it would have to be the rear derailuer getting worn out. Good luck.

  4. #4
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    That sounds like the problem I am having. I tried tensioning the spring last night and moving it to a tigher adjustment hole. It felt good in the driveway, but I'll test it on the trail today.


    The hub is a fairly new (3 month old) Hadley. I am waiting on a pin spanner to make sure the assembly is tight.

  5. #5
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    update

    I rode this morning and tightening the spring helped but did not totally fix the slipping feel/sound. I notice the problem only when accelerating out of hard turns or climbing on short steep rough climbs that require a sprint. Pretty much when the suspension is compressing and as I start to push hard on the cranks from a short coast.

    I have also noticed the chain is jumping from the middle ring to the granny ring more often (no large ring).

    I am thinking more and more its a chain tension problem and that its probably time to shop for a new RD.

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