Centaur Compact Chainset - chainline issues

leonlikestrees
leonlikestrees Posts: 528
edited October 2013 in Workshop
Hi all,

To be honest, I'm not sure how anyone will be able to help me with this, but it's driving me bonkers, so at least I can express my frustration here.

I've got a centaur compact chainset, square taper vintage.

I've got the 111mm centaur BB, and the chainline is just not right.

I need to shift about halfway up the cassette if I'm in the inner ring before the chain stops catching on the big ring.

I tried putting a 2.5mm spacer from a hollowtech 2 BB on the drive side to push it over a bit, but it didn't fix the issue (improved a little though).

now the confession on the weird bits.

I'm running FSA 48 outer, Shimano 34 inner ring.
it's a 135mm rear end (cross bike), with a SRAM 9spd 12-26 cassette.
gears are Dura-Ace 9spd vintage, except front mech which is a CX70.

so, although there's a bunch of random stuff there, it should all work together I think. No idea why it's not working. Any ideas?

Oh, and for what it's worth, the chainset I took off was a Dura-ace 7410 running 48/38 rings. This is all in the name of getting that lickle 34t ring for the race at the weekend, which has a steep little climb in it...

Comments

  • leonlikestrees
    leonlikestrees Posts: 528
    LOL, I should have known. It's straight up craziness, and there's no fix apart from going closer ratio on the chainrings, or getting a longer BB.
  • pinno
    pinno Posts: 52,329
    I had a similar problem with my Pinarello. The gap between the chainset and chainstay was so small that the chainring bolts made contact with the chainstay, I elected to get the 115.5mm BB. That is the only thing I can suggest.
    That 4.5mm should make all the difference without use of a spacer.

    It all came out when I upgraded to Record and used overboard cups; not much use to you though :D

    This ?!
    seanoconn - gruagach craic!
  • fortyone
    fortyone Posts: 166
    Make the chainrings slightly further apart - thin spacers.
  • pinno
    pinno Posts: 52,329
    fortyone wrote:
    Make the chainrings slightly further apart - thin spacers.

    ...and have problems shifting to the big chainring? Also, the bolts are recessed and it would be a tricky thing to do.
    seanoconn - gruagach craic!
  • fortyone
    fortyone Posts: 166
    No it isn't - easy thing to do - I have exactly the same chainset. You get nothing for not trying.
  • leonlikestrees
    leonlikestrees Posts: 528
    no problems with the chain slipping down between the chainrings?

    What did you use for spacers?
  • cycleclinic
    cycleclinic Posts: 6,865
    Centaur should require a 111mm ISO BB but it is the 135mm spacing that is giving you the issue. FSA for example have a warning in there tech docs that if the SLK compact chainset is used on a 135mm frame then chain rub on the big ring can be an issue. A longer BB axles will correct the chainline.

    Chainring spacer are not the answer as you would have to move both rings out by 2mm or so and that will never work out well.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.
  • leonlikestrees
    leonlikestrees Posts: 528
    that's why i thought the holowtech 2 bb spacer would fix the issue on the drive side, buit it didn't. I need more than 2.5mm?
  • cycleclinic
    cycleclinic Posts: 6,865
    2.5mm should have been enough did it make it better or did it not make any difference.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.
  • leonlikestrees
    leonlikestrees Posts: 528
    A bit better, but not good enough that i felt cpnfident racing. I need to do some more experimentation at the weekend, and probably some careful measurements

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