new rear mech needed?

piggy600
piggy600 Posts: 23
edited October 2008 in MTB workshop & tech
Hi all,

i have just replaced some old equipment - shimano deore 7 speed shifters for lx rapid fire 9 speed, deore 7 speed cassette to sram 950 9 speed 11t - 34t cassette,and sram 951 chain, but i have left on the shimano xt RD-m750 rear mech!

now after the first ride out tonight the rear mech is jumping about, got home washed off, and it all still seems to be set up correct, but to be honest i was struggling to get chain on the 34t rear sprock before i went out and onto the 11t rear, also the shifter for rear seems a bit slack,also rear mech seems very close to rear cassette.

now am i correct in chasing a set up issue, or have i overlooked some thing else like uncompatible rear mech.

cheers stu.

Comments

  • nicklouse
    nicklouse Posts: 50,675
    well you need to change the shifters back to 7sp (or 8 and not use one click) 9sp are not compatible. and you will also need a 7/8spd chain.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • ok, but what is not campatible, do i need new ream mech or will sram not work with shimano, old stuff is knackered so im upgrading as i go.

    stu.
  • nicklouse
    nicklouse Posts: 50,675
    the 9 spd stuff will not work with the 7spd stuff.

    So as i said bin the chai and the shifters.

    7 (or 8sp) shifter and 7/8spd chain.

    the problem is your shifters and the chain.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • sorry dont think ive explained,
    i have now upgraded to the following:

    shimano lx 9 speed shifters,

    sram 950 9 speed 11t - 34t cassette

    sram 951 9 speed chain,

    and a shimano lx rear mech.
  • nicklouse
    nicklouse Posts: 50,675
    Ok then your hub must have been a 8/9spd already and you have now removed the "7spd" spacer that allowed the use of the 7spd cassette?

    Or have you forced a 8/9spd hub into a 7spd frame?

    if you have reset the stops the mech will be fine but as the chain is thinner and if the jockey wheels are worn they may be having issues with the chain. change them to 9spd jockey wheels.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • I reckon it's more to do with the stops not set correctly, can't get into bottom or top gear is the main issue reported.

    Also the B screw setting may be causing some problems. Back off the 'angle of dangle' to increase distance between top jockey wheel and 34 tooth cog.
    --
    Burls Ti Tourer for Tarmac, Saracen aluminium full suss for trails
  • nicklouse
    nicklouse Posts: 50,675
    andrewjoseph
    very posible.

    I love list they are so much easier to follow.

    first time around i totally missed the change to 9spd cassette even though i read the post more than just the normal once.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • bought a new xt rear mech,

    got rear mech, set it up, worked spot on for frirst half an hour, then it was jumping every where,

    got back washed it, and the tension was really slack,

    the wire has not slipped on the rear mech, but the rear shifter seems to be not holding tension, so its time to strip them down i think.

    stu
  • supersonic
    supersonic Posts: 82,708
    Cables stretch and bed in from new, or settle back into the stops if you have removed them. Just add more cable tension.
  • stumpyjon
    stumpyjon Posts: 4,069
    Quite normal for the ferrules to not bed in properly on the cable ends until the cables have been put under tension a few times. Just do as Sonic says and adjust the barrel adjusters on the shifters.

    The old mech should have been fine, the mechs themseleves are dumb, it's the shifters that define where the mech stops.

    Did you reset the end stop screws and B screw with the other mech?
    It's easier to ask for forgiveness than for permission.

    I've bought a new bike....ouch - result
    Can I buy a new bike?...No - no result