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  1. #1
    mtbr member
    Reputation: Bloated Badger's Avatar
    Join Date
    May 2007
    Posts
    18

    New chain jaming why?

    Hi,
    I have just fitted a new sram PC-971 chain using the same number of links as my old chain and it shifts fine on the work stand, but as soon as i ride the bike and put any force into the pedals the rear mech pulls forward and the chain jams.
    Help what have I done wrong?
    The rest of the drive train is all Shimano XT.
    Cheers.

  2. #2
    Vaginatarian
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    Join Date
    Oct 2005
    Posts
    5,685
    Quote Originally Posted by Bloated Badger
    Hi,
    I have just fitted a new sram PC-971 chain using the same number of links as my old chain and it shifts fine on the work stand, but as soon as i ride the bike and put any force into the pedals the rear mech pulls forward and the chain jams.
    Help what have I done wrong?
    The rest of the drive train is all Shimano XT.
    Cheers.
    the chain is jamming because the old chain was worn out long ago, since it was worn out it gets longer( pins and connector getting sloppy) chains are steel, chain rings are aluminum, if you look at the chainring (middle especially) you will see that the teeth are now hook or U shapped, whats happening is the new chain doesnt fit the chainring propoerly and when it goes around it doesnt release (this is called chain suck) you should change your chain as soon as it "stretches" more than 1/16" per foot, pin to pin
    if you do that you should get 2-3 chain rings per chain. This also applies to the cassette but the cassette will get more like 4-5 chains because the wear is spread out over more gears

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