• Hi guy's, strange one here I'm hoping someone can help with.

    I'm running sram xx1 and have just replaced chain/cassette/chainring, riden 80miles on it and had no problems.

    I was racing today and the chain jumped behind the cassette, it then happened again about 5 min's later. I wondered if the mech hanger had been knocked so I avoid higher gears. As I'm riding middle of the block it was still jumping behind the cassette.

    The hanger isn't bent and the limit screws are all good. I wondering if it could be the Jockey wheels that are worn and causing it to jump so much? The course was extremely rough. Back on road the shifting is faultless??

    Any suggestions greatly appreciated as I've just lost out on double points and next race in 4 days, thanks!!!

  • it is always jumping on same cogs or random?

  • when you say jumping do you mean slipping on the cog or going from one cog to another?

  • It was random, I would be riding in say 5th and then the chain would jump between the cassette and the spokes

  • weird -
    have you got enough tension on the chain?
    some rear mechs for off rd have clutches too to stop things mashing about i think

  • have you check cables..? do they run free? not kinked? not grimy inside and catching...?

  • Xx1 clutch mech and new cables, I've a mechanic but never seen this which makes it worst

  • maybe the wheel is fucked...could the axle be snapped inside the hub?

  • Photos would make it easier

  • I've had a similar thing in the past and it was that one of the links was bent.

    If it's not that then, which of the parts of the drive train are new?

  • Was just going to suggest a twisted link

  • Also maybe a bent tooth on the sprocket(s)?

  • It's a through axle so hub is fine, new chain, cassette and chainring with 80miles on them. The only moving part that isn't new are the jockey wheels.

    I've spun the crank backwards across some gears to see if there's any noise/movement but nothing.

  • Still worth double checking for a twisted link I'd say,
    Jumping from the middle of the block to behind the largest sprocket is a big jump

  • it's weird cos if the mech hanger is straight, the limit screws are properly set, and the hub is straight in the dropouts then the mech shouldn't be able to put the chain behind the cassette

  • sometimes the end cap on the hub comes lose and the whole free hub assembly walks up and down the axle. Worth checking for lateral play in the cassette.

    But yeah going from 5th to over the block is a bit extreme.

    Is it a full sus frame?

  • Glad this thread popped up as I'm having the same thing happen on my cross bike.

    I thought maybe the derailleur cage is bent?

  • Spinning the cranks back would reveal a twisted link.

    Had the wheels off yesterday and check the cassette for play and nothing.

    It's a hardtail

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    • IMG_20190427_195406.jpg
  • Is this happening only whilst pedalling?

  • no damage to frame - chain / seat stays you've not noticed? that might account for it being fine unless knocked about on rough ground

  • Only while pedaling, ridden on road after the race and had no problems

  • What chain is that?

  • Did you replace the cable?

  • new cables.

    What cables? is it campag/sram? did you bed in the housing etc.?

  • Could it have been something that got stuck in the drivetrain? Perhaps whatever it was dislodged after the second jam?

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Chain jumping on a new cassette xx1 system - obvious solutions checked

Posted by Avatar for sjse @sjse