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Rear derailleur

rs6mra1rs6mra1 Posts: 104
edited July 2015 in Workshop
I changed my chain this morning and I cannot get the chain to seat on the largest cog on the cassette.
I have adjusted the H & L screws but when i turn them they do not move. Is it possible that the chain might be too long or is the cable too tight. I measured the chain against the old one so I am guessing it not the chain length.
Also when it is on the smallest cog at the rear the chain keeps rolling over the smallest cog and sometimes comes off but i put this down to not being able to adjust the derailleur using the 2 screws.
Any suggestions would be most welcome.


  • nicklousenicklouse Posts: 50,675 Lives Here
    If all you have done is replace the chain then things should work fine.

    If you have fitted it correctly and the cassette is not worn out and the chain is the correct one.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • jgsijgsi Posts: 5,038
    Are you getting the H and L screws the right way about?
    H will set the limit of travel furthest away from the spokes and L screw the amount of travel nearest the spokes.
  • lesfirthlesfirth Posts: 1,286
    Look at YouTube.
  • rs6mra1rs6mra1 Posts: 104
    I had to adjust the cable and then the H&L screws and finished of indexing. Done a couple of miles and all seems fine and I'll be heading out for a longish ride shortly
  • rs6mra1rs6mra1 Posts: 104
    As mentioned earlier i changed the chain at the weekend. I measured the new chain up against the new chain before taking 3 links off. From the picture below am i right in thinking the chain should be shorter? Or is it possible that my cable has stretched?
  • keef66keef66 Posts: 13,123
    That chain looks far too long, so it suggests the old one was too.

    Standard Shimano chain sizing advice for a double chainset is to thread the chain round the big chainring and biggest sprocket, but not through the rear mech, and then add one complete link (inner + outer).

    Obviously thread it through the rear mech properly before joining it. Using a KMC quick link is easier than the Shimano snap-off joining pin. Whatever you do, don't be tempted to rejoin it by reinserting a pin you've partially pushed out.
  • rs6mra1rs6mra1 Posts: 104
    Thanks for confirming.
  • apreadingapreading Posts: 4,533
    If you use the old chain to check the appropriate length, do so by counting the number of links, not comparing length - because the old one may/will have lengthened due to wear. So if you just go by the length of the old one, you may have one link too many. Having said this, if the old one was running, then the new one should too.

    That chain does look way too long though.
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