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Stronglight rings on Shimano 5750 crank problem

dieselgeezerdieselgeezer Posts: 229
edited September 2016 in Workshop
Replaced worn Shimano rings with Stronglight on a 5750 compact. Now have the issue of chain rubbing the inner face of the 50 ring when in the 34 and on the 12,13 &14. I expected the rub in the 12 but not the 13 & 14. With the original Shimano rings there was only rub in the 12. I suspect the Shimano outer was a bit wider so that it was positioned further out. Can anyone suggest a solution?
-- "I am but a spoke in the wheel of life" -- Ghandi

Posts

  • imposter2.0imposter2.0 Posts: 11,382
    Re-think your gear selection? It's not generally good practice to be that far down the block when on the inner ring, for the reasons you describe...
  • Really trying to suss why the original set-up worked on the 13 & 14 & why the Stronglight rings don't.
    -- "I am but a spoke in the wheel of life" -- Ghandi
  • imposter2.0imposter2.0 Posts: 11,382
    The teeth may be taller, slightly wider, or just less worn.
  • I've measured the thickness of the 5 fixing lugs on the 5750 & they are 3.5mm. Also measured the thickness of an old FSA & Stronglight crank & they're also 3.5mm. All inner rings I have are the same thickness but it appears that the culprit in all of this is the outer ring. The Stronglight 50 is quite thin compared to the original Shimano; the latter has lots more "meat" on the inner face which makes the gap between the inner & outer rings larger & so minimizes the chain rub problem.
    I also found an old pair of Sram rings which have similar thicknesses to the Stronglight ones; these too caused chain rub in the 12, 13 & 14.
    So, it appears I should have bought Shimano replacement rings, not Stronglight.
    -- "I am but a spoke in the wheel of life" -- Ghandi
  • imposter2.0imposter2.0 Posts: 11,382
    Either way, you would be better off not running those gear combos. Shift up on the front a bit earlier and the issue will disappear.
  • keef66keef66 Posts: 13,123
    Do your new rings have a right and a wrong way round? Most are installed with any markings facing outwards away from the bike.
  • Rings definitely fitted the correct way. The outer will only fit one way due to pin adjacent crank arm. The inner also only fits one way due to recessed edge to holes for fixing bolts.
    -- "I am but a spoke in the wheel of life" -- Ghandi
  • crankycrankcrankycrank Posts: 1,830
    You can buy spacer shim washers that fit on the inside of your 50t ring on the chainring bolts. They come as thin as .6mm (which usually works for a problem such as the OP's) to a few mm wide. Problem solved. Ask for them at a good LBS or shop the net. http://www.ebay.co.uk/itm/Chainring-Bol ... 0571843676
  • An update. Did as "Crankycrank" suggested & put 1.0mm thick washers behind the big ring. Works a treat. Can use the 13 & 14 with no rub at all & no floating chain issues going from big to small ring.
    Big thanks for the suggestion!
    -- "I am but a spoke in the wheel of life" -- Ghandi
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