Chain "jumping" on rear cassette

scotthunter Posts: 140
edited May 2018 in Workshop
I've got a problem with chain jumping around on my cassette on my Giant Defy. Bike is new (done 200 miles) and this is the second time I have had this problem. The first time I sent it back to the shop to get fixed, which solved the problem for a week or so, and now I'm having the same issue again.

Basically when I'm riding (i.e. torque is being applied through the pedals) the chain will hop around the middle sprockets on the cassette, in a rapid and violent manner. The drivechain is also noisy, like something is rubbing, and sometimes when I change to a faster gear it will skip a sprocket.

I have a Shimano Ultegra, 11x34 cassette and a Shimano Ultegra, 34/50 crackset. It's a full Ultegra R8000 groupset. All the components are brand new.

This is the third time I have had to go back to the shop because of gearing/braking issues and it's a 2 hour round trip for me so I am getting annoyed now. I think the gear issue is something to do with incorrect cable tension - is this normal for a new bike? The shop originally said to come back after 6-8 weeks for a first service but the bike is only 3 weeks old and it's practically unridable.

Thanks for your help.


  • haydenm
    haydenm Posts: 2,997
    Cable tension will change as the cable stretches and settles, very common/inevitable. Just twist the barrel adjuster until it stops doing it. There are loads and loads of bits on the internet about indexing gears to help you if you get stuck, aside from punctures it's probably the most common piece of maintenance you will do. Congratulations on the new bike, and try to enjoy learning the maintenance side even if it's a bit of a drag!
  • gazza1286
    gazza1286 Posts: 45
    You should also suggest to the bike shop that they should also check the rear derailleur hanger for correct alignment if they haven't yet considered that...
  • scotthunter
    scotthunter Posts: 140
    Thanks all, I will go back to the store and suggest these changes. I didn't expect this to happen twice in the first 3 weeks. It's so bad that I can't even ride the bike at the moment unless I use the same gear.
  • haydenm
    haydenm Posts: 2,997
    Gazza1286 might be onto something, if it's as bad as it sounds then that would explain it. In general with stretching cables you'll find it starts to skip gradually then get to that point if you don't tension it with the barrel adjuster, it's the sort of thing that you really need to be able to do yourself and it's a very simple 30 second job, it could happen fairly regularly on a new bike; if it's the hanger or derailleur that are bent then you have no hope of getting them running nicely.

    Having said all this, if it's just cable tension then you can sort it yourself and enjoy the learning process, if it's anything else then the shop really should have sorted it on the first trip. Maybe take it somewhere else if their mechanic can't fix it, it shouldn't be hard to diagnose for a bike mechanic at all