SRAM red chainset

jbwilliamz
jbwilliamz Posts: 187
edited October 2011 in Workshop
Hi,

Just a quick one; I've recently put a SRAM Red chainset (50/34) on my bike with 105 running gear (updating piece by piece).

It's a 68mm BB shell width. I haven't put any spacers in the BB but there seems to be some rubbing on the front derailiur when (I know I shoudln't) the chain runs from the two extreme positions (High-Low and Low-High).

Any suggestions? Would spacers make a difference?

I've actually got a 38T ring to put on the bike as the 34T is waaay too "spinny".

Comments

  • Pseudonym
    Pseudonym Posts: 1,032
    it won't be the spacers (you don't need them anyway) - it should just be a matter of fine-tuning the front mech. In my experience, cable tension is fairly critical on Sram mechs, and I remember re-tensioning my cable a few times and twisting the limit screws before it ran ok. I can now run full crossover with no rubbing, although I tend not to if I can help it...
  • jbwilliamz
    jbwilliamz Posts: 187
    Sorry, I'm using a Shimano 105 front mech with the SRAM chainset.

    Would that be a cause? Are the SRAM mechs wider?
  • Pseudonym
    Pseudonym Posts: 1,032
    my mistake - either way, it should be just a fine tuning issue...
  • LongIslandTom
    LongIslandTom Posts: 51
    jbwilliamz wrote:
    It's a 68mm BB shell width. I haven't put any spacers in the BB but there seems to be some rubbing on the front derailiur when (I know I shoudln't) the chain runs from the two extreme positions (High-Low and Low-High).

    Sounds normal to me. Whenever you crosschain big-big or small-small, some chain-rub is to be expected if your derailleurs are adjusted properly.

    And yes, you shouldn't run crosschained if you can avoid it.
  • Yossie
    Yossie Posts: 2,600
    As avove - just a setting up thing.

    As I am evil I do also tend to run big/big occasionally (have done so on Red, Dura Ace, Shytegra and 105) but have everything set up so that it doesn't rub: just a matter of fine tuning.

    And don't worry - you won't burn in hell for running big/big. :twisted:
  • jbwilliamz
    jbwilliamz Posts: 187
    Cheers lads. Will play around with the setup and see if I can get it to work without rubbing.
  • mikenetic
    mikenetic Posts: 486
    Might be stating the bleeding obvious here.

    If you're running 105 STIs then the lever for the front mech has that funny little half-click that moves the cage in a little bit, with the full click dropping the chain from the large to small ring up front.

    If it's set up properly then you shouldn't have any issues with rubbing even fully crossed up on big to big as that little click seems to give plenty of space for adjustment.

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