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What cog should I not get chain rub?

Darce87Darce87 Posts: 6
edited July 2014 in Workshop
Morning all,

When I'm in the big chain ring, what cog should I stop getting chain rub on the front derailleur? I've noticed I'm still getting some rub when I'm in the 3rd cog on cassette. Should I adjust the cable tension slightly? I feel like the chain isn't crossing at this point.

Thanks

Posts

  • sungodsungod Posts: 12,208
    setup aside, it can vary with geometry and components, for instance on mine i can cross chain all the way without getting any chain rub

    do you mean the third biggest sprocket and the chain rubbing on the lefthand side of the cage?

    in that case the cage may be sitting too far out (try using the limit screw to adjust), but it could also happen if the cage isn't installed parallel or is bent

    might be worth looking at the install/adjustment guide for the specofic front mech and go through it from scratch
    my bike - faster than god's and twice as shiny
  • Darce87Darce87 Posts: 6
    Yes, 3rd biggest sprocket and rubbing on the inside edge of FD
  • ai_1ai_1 Posts: 3,060
    What groupset are you using and assuming it has it, are you using the front derailleur trim?
  • Darce87Darce87 Posts: 6
    shimano sora
  • ai_1ai_1 Posts: 3,060
    Darce87 wrote:
    shimano sora
    Really going with the minimumof info here aren't you?
    Current or older model? (i.e. 8 or 9 speed), Does it have trim and do you use it?
  • Darce87Darce87 Posts: 6
    2013 9 speed. I don't know if it has trim. IT clicks twice when shifting to small chain ring, so I guess so?
  • ai_1ai_1 Posts: 3,060
    edited July 2014
    The purpose of the trim is to move the front derailleur in slightly (without moving the chain) when using the larger sprockets to eliminate chain rub. So it sounds like your groupset comes with a ready-made solution to your problem. If you shift to a large back sprocket and are getting chain rub then engage the trim (normally a gentle click part way through a normal gear change) to engage the trim and move move the derailleur away from the chain.
  • Darce87Darce87 Posts: 6
    I'll give it a go!
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