chain rubbing on chainring

chrb8
chrb8 Posts: 38
edited October 2011 in Workshop
Hi,
On my winter bike I have a nine speed Tiagra setup with a compact FSA chainset. I have noticed that when in the smaller front ring the chain rubs against the inside of the big ring when using gears 6 and above at the back.

Is there anything I can do to help stop this?

(Obviously changing up to the bigger ring is the main thing to do, but sometimes on rolling roads I like the flexibility of having more gears in the small ring and keeping a higher cadence)

Comments

  • A longer axle on your bottom bracket? :wink:
    jedster wrote:
    Just off to contemplate my own mortality and inevitable descent into decrepedness.
    FCN 3 or 4 on road depending on clothing
    FCN 8 off road because I'm too old to go racing around.
  • ForumNewbie
    ForumNewbie Posts: 1,664
    chrb8 wrote:
    Hi,
    On my winter bike I have a nine speed Tiagra setup with a compact FSA chainset. I have noticed that when in the smaller front ring the chain rubs against the inside of the big ring when using gears 6 and above at the back.

    Is there anything I can do to help stop this?

    (Obviously changing up to the bigger ring is the main thing to do, but sometimes on rolling roads I like the flexibility of having more gears in the small ring and keeping a higher cadence)
    Are you sure it's not rubbing against the front mech? Can't see how it would be rubbing against the big chain ring unless something was seriously wrong with alignment of chain rings.
  • Twostage
    Twostage Posts: 987
    You could try a sturmey archer sprocket spacer to push the bottom bracket out a few mill.
  • chrb8
    chrb8 Posts: 38
    Are you sure it's not rubbing against the front mech? Can't see how it would be rubbing against the big chain ring unless something was seriously wrong with alignment of chain rings.

    Yeah I thought that at first, but when I went to check the front mech alignment I realised it was the inside of the big ring it's rubbing on
  • Gary D
    Gary D Posts: 431
    Another shot in the dark.....check that your chain is actually for 9 speed and not 8.

    I have a triple with 9 speed mechs, front chainring and chain - although the cassette is only 8 speed. I recently noticed I had a crack in one of the side plates of the chain, so as an emergency fix, I put on an 8 speed chain.
    Although it works OK, it rubs when on the top 2 or 3 gears when using the middle ring which it didn't do before.

    Only conclusion I came to is that it is because the 8 speed chain is wider.

    Hope this helps.
    Gary.
    Oh and I feel like I've been raped by an Orangutan :shock: And I've got legs like Girders :lol:
  • elcani
    elcani Posts: 280
    I've had bikes that do this, but only on triples and only when in the smallest sprocket at the back. For it to be rubbing in smallest three or four sprockets suggests your bottom bracket is too short. Is it the original set-up? Square taper bottom bracket?
  • apreading
    apreading Posts: 4,535
    My boardman hybrid does this - because the double has such a big step up from 36-50 I think, it means that the big ring gets in the way of the route from small ring to the smallest few sprockets. I assumed it was fairly normal? Cant see how it would be avoided except with a smaller big ring or a spacer between the two rings (therefore meaning it wouldnt be a compact anymore)?
  • Twostage
    Twostage Posts: 987
    Twostage wrote:
    You could try a sturmey archer sprocket spacer to push the bottom bracket out a few mill.
    You get them here :- http://www.sjscycles.co.uk/sturmey-arch ... 7-prod512/

    I know it doesn't sound right but you just take off the BB. Stick the washer on the BB on the drive side a re-assemble. It will push the BB (and hence the chainrings) outboard by 1.6mm which might be enough to stop the rub as the inner chainring will be more in line with the outer sprockets of the cassette. As they are only 2 quid you could get 2 then you'd have 3.2 mm to play with.
  • chrb8
    chrb8 Posts: 38
    Gary D wrote:
    Another shot in the dark.....check that your chain is actually for 9 speed and not 8.

    I have a triple with 9 speed mechs, front chainring and chain - although the cassette is only 8 speed. I recently noticed I had a crack in one of the side plates of the chain, so as an emergency fix, I put on an 8 speed chain.
    Although it works OK, it rubs when on the top 2 or 3 gears when using the middle ring which it didn't do before.

    Only conclusion I came to is that it is because the 8 speed chain is wider.
    .

    I have recently put a new chain on the bike and, while it is definitely a 9 speed chain, this does raise another question... The chain I put on is a SRAM one rather than a Shimano, which I assumed would be suitable - but maybe this could be part of the problem??? Any thoughts?
  • Was it doing it before the chain swap? If not, you`ve probably hit the nail on the head.
    Jens says "Shut up legs !! "

    Specialized S-Works SaxoBank SL4 Tarmac Di2
  • mikenetic
    mikenetic Posts: 486
    chrb8 wrote:
    Gary D wrote:
    Another shot in the dark.....check that your chain is actually for 9 speed and not 8.

    I have a triple with 9 speed mechs, front chainring and chain - although the cassette is only 8 speed. I recently noticed I had a crack in one of the side plates of the chain, so as an emergency fix, I put on an 8 speed chain.
    Although it works OK, it rubs when on the top 2 or 3 gears when using the middle ring which it didn't do before.

    Only conclusion I came to is that it is because the 8 speed chain is wider.
    .

    I have recently put a new chain on the bike and, while it is definitely a 9 speed chain, this does raise another question... The chain I put on is a SRAM one rather than a Shimano, which I assumed would be suitable - but maybe this could be part of the problem??? Any thoughts?

    I doubt that would be the issue - I've run SRAM chains on Shimano 9 & 10 speed setups (Tiagra, 105), using both FSA and Shimano chainsets, without issue.