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rear mech prob ? or chain since visit to lbs

bambabamba Posts: 856
edited February 2010 in MTB workshop & tech
hello, urgent help needed on my mates 2009 spec pitch comp',before tomorrow ladybower trip out.
was fine before a 6 month service and now first use since the rear mech is in unusual postion when on both smallest cogs front an rear,i no this combination should not be used, but the rear mech is tryin to wrap it self around the back end, the chain appears very slack, the bike is about 9 months old an not realy had a lot of use, prob about once a month.
rear mech is a sram x7, just noticed part of the mech is resting against and part worn a plastic stop on the main body, when compaired to his ht with a sram x 4 the rear mech is no where near this plastic stop when on the smallest cogs,
its almost as though the chain has grown a few links, incidently all the chain links are marked shimano hg apart from 3 seperate spaced out links marked FJ ???
here is a pic ... 010320.jpg


  • supersonicsupersonic Posts: 82,708 Lives Here
    As you say, a gear that you should not be using! That is the reason why that is happening.

    If the chain is measured correctly for the big/big (again, should not use, but if you do change into this and it is too short you will cause catastophic damage) thenm you can solve it by using a rear mech with greater capacity. It will flap about more though.
  • bambabamba Posts: 856
    hmmm, not got time for new rear mech, just tried taking some links out but took too many, too short now
  • supersonicsupersonic Posts: 82,708 Lives Here
    What chainset do you have, a double or triple?

    Chainlength should be measured by wrapping the chain around the two largest cogs, and adding two links, bypassing the mechs. This is for safety reasons as described above.

    You can go shorter, but don't use that gear!
  • bambabamba Posts: 856
    in the proccess of puttinthem back now, was still too short with 2 links out,
    think it will be a case of leave how it was an cross fingers tomorrow,
    its triple by the way, not sure of the chain set , sorry to be short but bit desperate and not to familure with this kind of stuff, in at the deep end with no time
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