Chain Rubbing

greeg
greeg Posts: 41
edited July 2007 in MTB workshop & tech
Folks,
i've had to buy a new front mech but i'm having dificulty in
getting the chain to stop rubbing on the outer cage when on the 6th and 7th
sprockets.
I'm running 7 speed but it's an M761 front mech.
Anyone offer advice on the solution?

Regards.

Comments

  • supersonic
    supersonic Posts: 82,708
    I think we have spoke before! The mech is narrower, so you may find it takes more fine tuning. Park has a great guide on set up from scratch. You may find that you eliminate rubbing in this extreme with say the H stop wound out and more tension, then it wont shift down well. You may have to compromise. I have been known to gently bend the mech plates apart with a screwdriver, but I didn't tell you that... ;-)
    GT ZASKAR CARBON TEAM

    VOODOO CANZO

    Come and see me at https://www.facebook.com/biketyke/
  • greeg
    greeg Posts: 41
    Yeah,i was assured against my better judgement by my LBS that it would work no bother.I feel like taking it down and wrapping it round his head as i've spent a lot of time on it.I can compromise by not using the 6th and 7th sprockets,but i don't want to do that.
    What would fitting a 9 speed chain do?
  • supersonic
    supersonic Posts: 82,708
    9 speed chain is narrower, but is 99% likely not to work with your chainrings, so I would advise against this. I have been in the same situation before when I was a mechanic, they need to be set up to the absolute fraction of a millimetre, and even then slight rub is noticable sometimes. Maybe the shop could try?!
    GT ZASKAR CARBON TEAM

    VOODOO CANZO

    Come and see me at https://www.facebook.com/biketyke/
  • greeg
    greeg Posts: 41
    My chainset's an XT M761 Hollowtech.Do you mean it won't mesh with the sprockets?
  • supersonic
    supersonic Posts: 82,708
    Interesting mix of components! The chainset is indeed 9spd compatible, and in many circumstances a 9psd chain will work fine on 7 and 8 spd sprockets. But a 9spd chain will not work on true 8spd chainrings (nor 7spd). But there is only one way of guaranteeing a set up that is going to work the best, and that is to use all the same parts ie all 9 or 8 (or 7spd). Depending on wear of sprockets and cassette, a new chain might not take and will skip.

    Many new 8spd bikes now have 9spd chainsets because they work absolutely fine with 8spd chains. But they have 8spd front mechs! My advice would be to persevere with the set up or get an alivio front mech.
    GT ZASKAR CARBON TEAM

    VOODOO CANZO

    Come and see me at https://www.facebook.com/biketyke/
  • greeg
    greeg Posts: 41
    I think i'll just take it back and get a dedicated 7 speed.If the LBS wants to argue that it's been used,i'm ready for them.Cheers
  • greeg
    greeg Posts: 41
    Exchanged the XT for an Alivio mech and all is well.Thanks for the feedback
  • ED209
    ED209 Posts: 174
    Doesn't sound like a fair swap?!?

    :shock:
    <font size="1">GT Aggressor XC2 - lovingly crafted by the artisans at Halfords with the addition of XT hydraulic brakes, M520 pedals, Ritchey Ergo foam grips and my old nice and comfy Spesh BG saddle</font id="size1">
  • greeg
    greeg Posts: 41
    Got the difference in price back as i'd bought it on their advice.
  • ED209
    ED209 Posts: 174
    Oh OK - nice one :lol:
    <font size="1">GT Aggressor XC2 - lovingly crafted by the artisans at Halfords with the addition of XT hydraulic brakes, M520 pedals, Ritchey Ergo foam grips and my old nice and comfy Spesh BG saddle</font id="size1">

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