Transmission service problem

Discussion in 'Mountain Bikes' started by Johns, Mar 23, 2003.

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  1. Johns

    Johns Guest

    On a XT 9-sp transmission set-up I've just replaced the chain (following HG failure) with a PC59
    item plus I've renewed the middle front ring. Got the chain length right and gears shift nicely on
    the bench. Under load (even fairly light) on the road/trail the chain is jumping. Not between gears
    just within same gear. Can't work out exactly how and where. Jockey wheels are fairly new, cassette
    less so but doesn't appear very worn - hard to tell without a fresh one to compare. Wonder if I've
    bent the mech at some point. Cage isn't dead vertical (slightly angled in) when in most gears. Would
    you expect to replace the cassette with each chain? John S
     
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  2. Andy Chequer

    Andy Chequer Guest

    "JohnS" <.@.com> wrote in message news:b5ke97$29g$1@hercules.btinternet.com...
    > On a XT 9-sp transmission set-up I've just replaced the chain (following
    HG
    > failure) with a PC59 item plus I've renewed the middle front ring. Got the chain length right and
    > gears shift nicely on the bench. Under load (even fairly light) on the road/trail the chain is
    > jumping. Not between gears
    just
    > within same gear. Can't work out exactly how and where. Jockey wheels are fairly new, cassette
    > less so but doesn't appear very worn - hard to tell without a fresh one to compare. Wonder if I've
    > bent the mech at some
    point.
    > Cage isn't dead vertical (slightly angled in) when in most gears. Would you expect to replace the
    > cassette with each chain? John S

    Replace the casette and all will be well. I know people who can get away with chainging just the
    chain fairly regularly but it has never, ever worked properly for me.

    Andy Chequer
     
  3. On Sun, 23 Mar 2003 13:53:43 +0000, did issue forth:

    > On a XT 9-sp transmission set-up I've just replaced the chain (following HG failure) with a PC59
    > item plus I've renewed the middle front ring. Got the chain length right and gears shift nicely on
    > the bench. Under load (even fairly light) on the road/trail the chain is jumping. Not between
    > gears just within same gear. Can't work out exactly how and where. Jockey wheels are fairly new,
    > cassette less so but doesn't appear very worn - hard to tell without a fresh one to compare.
    > Wonder if I've bent the mech at some point. Cage isn't dead vertical (slightly angled in) when in
    > most gears. Would you expect to replace the cassette with each chain? John S

    It's probably the cassette. You'll be very lucky if you manage to get a new chain to work with an
    old cassette.

    --
    Huw Pritchard Replace bounce with huw to reply by mail
     
  4. David Kunz

    David Kunz Guest

    JohnS wrote:
    > On a XT 9-sp transmission set-up I've just replaced the chain (following HG failure) with a PC59
    > item plus I've renewed the middle front ring. Got the chain length right and gears shift nicely on
    > the bench. Under load (even fairly light) on the road/trail the chain is jumping. Not between
    > gears just within same gear. Can't work out exactly how and where. Jockey wheels are fairly new,
    > cassette less so but doesn't appear very worn - hard to tell without a fresh one to compare.
    > Wonder if I've bent the mech at some point. Cage isn't dead vertical (slightly angled in) when in
    > most gears. Would you expect to replace the cassette with each chain? John S
    >

    If it skips no matter which front chainring, then replace the cassette. If it skips only on one
    front chainring, start with replacing that chainring (and then probably the cassette :)).

    The problem is the chain "stretches" (not really... but, wear makes the links further apart). This
    wears the gears for a different chain link spacing. When you put the new chain on, each link does
    not bear the load because the gear spacing has been worn too far apart. It skips.

    I can usually get 3 chains to a cassette, and 3 or 4 to a middle or small chain ring. I replace the
    chain when the spacing of 6 links is 6-1/16" (it's supposed to be 6"). You can get more life out of
    the chain, but not without replacing gears more often. YMMV.

    Some people buy 3 chains with quick links (like the PC59) and rotate between them at each cleaning.
    This way, all 3 chains and the gears wear about the same.

    David
     
  5. Johns

    Johns Guest

    Thanks to all for the swift and considered reponses. Much as I thought. Rotating three chains seems
    a sound idea otherwise this sport is going to get even more expensive!

    Yours til me tyres wear out John S
     
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