Skipping Gears...

Mr OCD
Mr OCD Posts: 382
edited June 2011 in MTB workshop & tech
I can't figure out what I'm doing wrong ... the rear mech keeps skipping gears despite careful setup of gears via the Park Tools website.

All cables are free and set correctly
High and Low points are set correctly
Indexing set correctly
Rear cassette (SRAM) is clean and un-worn

I'm starting to think the chain could be to blame?

Any thoughts? - its a Shimano Alivio rear mech with Alivio shifter...

I'm considering binning the lot and fitting my SRAM stuff on the bike if I don't get this sorted!
2009 Carrera Fury

Comments

  • The Rookie
    The Rookie Posts: 27,812
    'Skipping' define please?

    Not shifting up a gear or not shifting down or genuinley skipping where (for example) you shift from 4th to 3rd and nothing happens then when you shift again it jumps straight to second?

    Simon
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • Mr OCD
    Mr OCD Posts: 382
    The Beginner wrote:
    'Skipping' define please?

    Not shifting up a gear or not shifting down or genuinley skipping where (for example) you shift from 4th to 3rd and nothing happens then when you shift again it jumps straight to second?

    Simon

    Sure... what you've said is spot on!

    In 1st gear ... (rear cassette) click to 2nd ... nothing happens... click again ... skips to third ...

    When riding ... sometimes it will stay in 3rd but then jump to 2nd and then go back to 3rd ...

    I have setup SRAM stuff spot on when swapping to bikes but this Alivio stuff (temporary) is driving me nuts ...
    2009 Carrera Fury
  • The Rookie
    The Rookie Posts: 27,812
    If I can set up a thumb click shifter and cheap 'SIS' mech on my beater, I'm sure alivio should work fine.....

    Have you set the B-screw, last time I had this issue the guide (top) pulley was too far from the cassette, also is the guide pulley good? It should move side to side slightly but not tilt.

    Simon
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • nicklouse
    nicklouse Posts: 50,675
    Mr OCD wrote:
    The Beginner wrote:
    'Skipping' define please?

    Not shifting up a gear or not shifting down or genuinley skipping where (for example) you shift from 4th to 3rd and nothing happens then when you shift again it jumps straight to second?

    Simon

    Sure... what you've said is spot on!

    In 1st gear ... (rear cassette) click to 2nd ... nothing happens... click again ... skips to third ...

    When riding ... sometimes it will stay in 3rd but then jump to 2nd and then go back to 3rd ...

    I have setup SRAM stuff spot on when swapping to bikes but this Alivio stuff (temporary) is driving me nuts ...
    sounds like friction in the cables as it is not releasing the cable.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Mr OCD
    Mr OCD Posts: 382
    The Beginner wrote:
    If I can set up a thumb click shifter and cheap 'SIS' mech on my beater, I'm sure alivio should work fine.....

    Have you set the B-screw, last time I had this issue the guide (top) pulley was too far from the cassette, also is the guide pulley good? It should move side to side slightly but not tilt.

    Simon

    Will check this tonight when get home (new tyres to fit anyway) but only ever adjusted the 'B screw once when I originally installed the rear mech on the bike ...
    2009 Carrera Fury
  • Mr OCD
    Mr OCD Posts: 382
    nicklouse wrote:
    sounds like friction in the cables as it is not releasing the cable.

    They are nearly brand new Clarke cables...
    2009 Carrera Fury
  • timpop
    timpop Posts: 394
    The Beginner wrote:
    If I can set up a thumb click shifter and cheap 'SIS' mech on my beater, I'm sure alivio should work fine.....

    Have you set the B-screw, last time I had this issue the guide (top) pulley was too far from the cassette, also is the guide pulley good? It should move side to side slightly but not tilt.

    Simon
    +1
    It might be worth starting again too. Undo the cable and go through the normal set-up process.
    Many happy trails!
  • pugaltitude
    pugaltitude Posts: 191
    They might be brand new cables but if they are not lubricated there will be slight friction.
    Mech hanger was the problem with my fury.
    You think its straight and its out by a ball hair.
  • bails87
    bails87 Posts: 12,998
    They could be new but be catching on a bit where they weren't cut cleanly. Worth double checking that the cable moves freely through the outer.
    MTB/CX

    "As I said last time, it won't happen again."
  • craker
    craker Posts: 1,739
    Is there any chance the chain is too long? I had this on my new road bike, the indexing was never quite there and the chain would slip in some gears.

    The mech wasn't able to keep enough tension on the chain -> take some links out and it's now running brilliantly.
  • Mr OCD
    Mr OCD Posts: 382
    Started again and adjusted the B screw properly this time ... it's made a big difference but still not quite perfect as is skipping a gear occasionally.

    Will try the chain next...
    2009 Carrera Fury
  • jamojaw
    jamojaw Posts: 89
    timpop said check your guide pulley too. I would check this too as that is also where i had a problem. the step screw had loosened and the chain would drag on most gears.

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