Rear Mech Slipping

steelo
steelo Posts: 542
edited May 2014 in MTB workshop & tech
I've just fitted a new chain and cassette to my MTB. I've adjusted the rear mech so the gears were changing sweetly in the dry conditions when out riding. However, last night it was ridiculously wet and muddy and the rear mech/chain was constantly jumping so it felt like every 2-3 pedal rotations the chain was slipping as though there were no teeth on the sprockets.

Is this a common thing to happen when the rear mech/chain gets muddy or is it an alignment issue?

I thought I had the rear mech dialled in nicely but after last night I'm doubting my abilities! Maybe I'm just out of touch with how a bike performs in the mud?

Rear mech - XT Shadow ('09)
Cassette - SRAM PG990 ('14)
Chain - SRAM PC991 ('14)

Thanks.
Specialized Rockhopper '07
Trek Fuel EX8 '09

Comments

  • cooldad
    cooldad Posts: 32,599
    Could be mud.
    Could be worn chainrings.
    Could be set up.
    Mechs don't slip though.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

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  • The Rookie
    The Rookie Posts: 27,812
    A favourite is mud between the cassette sprockets lifting the chain off the teeth.....that would fit your description perfectly.
    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.
  • iwilldoit
    iwilldoit Posts: 710
    Give it a good clean and take it for a ride if nothing else it will show you if it's the mud or not.
  • AlShack
    AlShack Posts: 38
    Mine did exactly the same after I'd fitted a new cassette/chain/cables etc. Had all worked perfectly for the first ride, then the second ride it was jumping all over the shop. However, I was axle-deep in mud on that ride. Once cleaned off, it was back to slick-shifting and staying in gear.

    Mud is evil, although quite good fun as well :)
  • cooldad
    cooldad Posts: 32,599
    The cable outers settle and compress a fraction, so after riding for a while you need to tweak the indexing.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • steelo
    steelo Posts: 542
    Cool thanks guys, I've cleaned it up so hopefully when I take it for a spin tomorrow it'll only need a slight tweak if anything. I think I may replace the middle chain-ring as well as it's had plenty of use and a new one will hopefully match up better with the new chain and cassette.
    Specialized Rockhopper '07
    Trek Fuel EX8 '09