Gear indexing, keeps jumping around....

gregwari Posts: 230
edited May 2020 in Workshop
Im having no end of problems with my gears / shift on my cassette. I'm not getting consistent shifting through the gears, either the shift is precise at the lower end but then starts skipping a shift / jumping 2 gears on the upper dogs or vice versa; whether it would high or low depends on the cable tension.
Cassette is newish as is the chain, I've redone the outer and inner cables too. Any other suggestions would be great


  • reaperactual
    reaperactual Posts: 1,185
    Generally sounds like some sort of excess friction in cables of some sort.

    Stiff links in the chain?

    Could be a slightly bend derailleur hanger?

    Inner cable correctly routed and anchored into mech?

    Was the inner cable in good condition?

    After fitting a new inner turned out it had a slight kink from bad packaging which was enough to cause similar problems.
  • tackleberry
    tackleberry Posts: 81
    Bent derailleur hanger?
  • reaperactual
    reaperactual Posts: 1,185
    Mountain bikes have them and pretty sure road bikes do too?

    Designed to be soft and break or bend easily to protect frame damage in case of rear mech displacement which is unusual but not impossible more so when mountain biking.

    Can be bent easily with a slight knock without being visible to naked eye but enough to cause these symptoms.
  • masjer
    masjer Posts: 2,555
    edited May 2020
    As suggested above- check the cable is mounted to the correct side of the derailleur clamp bolt.
    Were the outer cables cut cleanly and not crushed?
    Check the inner cable is routed through the bottom bracket guide correctly.
    Inspect (by removing cable) the that the derailleur moves freely- lube pivots if necessary.
    Check the length of the final loop of cable going to the derailleur is long enough.
  • lesfirth
    lesfirth Posts: 1,382
    I bought a hanger alignment tool. It does not get used often but saves a whole lot of hassle when it does.
  • gregwari
    gregwari Posts: 230
    Thanks for the advice, problem fixed. Mech hanger slightly loose, one of the cape on the outer cable housing was causing a little bit of friction and I'd fastened the cable into the wrong side of the derailleur bolt.
    Working lovely now... Just in time for the weather to turn crap....

    Thanks again