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Weird sticking chain problem

johngtijohngti Posts: 2,416
edited June 2018 in Workshop
Got the new r8000 groupset installed on my bike with the medium cage rear mech and the 11-34 cassette. Very happy with it but there’s one little niggly problem. When I stick the chain on the 27-tooth cog at the back, there’s a regular-ish point where the chain seems to stick very slightly before clicking into place. The click is very audible and obvious. No tight links in the chain which was also fitted new (kmc jobbie). Click happens whichever front ring it’s set to and it only happens on the 27-tooth cog.

Anyone seen that before? Any ideas on fixing it?

Posts

  • sandyballssandyballs Posts: 577
    I’ve only seen it when some of the teeth are slightly rotated as pick up teeth to smooth the changing of gears, these can catch when the chain is not perfectly aligned, barrel adjuster may help. If your sure it’s not sticking chain links.
  • johngtijohngti Posts: 2,416
    Thanks. I’ll have another look at that shortly. Is it possible that only that cog could be affected by it?
  • sandyballssandyballs Posts: 577
    I saw it once at the other end of a cassette only on the 11 tooth but it’s worth a quick check to discount it.
  • Vino'sGhostVino'sGhost Posts: 4,129
    2 thoughts,

    Check theres no burr on the cassette, file if there is.

    freehub, is it in good nick? if press fit bearings are they in and aligned properly and if spacer required is it there?
  • milemuncher1milemuncher1 Posts: 1,472
    Your top jockey wheel is too close to the sprockets on the cassette. Get yourself one of these.

    https://www.sigmasports.com/item/Wolf-T ... lsrc=aw.ds

    It moves the jockey wheels down and away from big sprockets in the cassettes. You may need a longer chain as well.
  • johngtijohngti Posts: 2,416
    2 thoughts,

    Check theres no burr on the cassette, file if there is.

    freehub, is it in good nick? if press fit bearings are they in and aligned properly and if spacer required is it there?

    I’ll check for number 1 next time I get it on a workstand. As far as number 2 goes, freehub is all fine.
  • johngtijohngti Posts: 2,416
    Your top jockey wheel is too close to the sprockets on the cassette. Get yourself one of these.

    https://www.sigmasports.com/item/Wolf-T ... lsrc=aw.ds

    It moves the jockey wheels down and away from big sprockets in the cassettes. You may need a longer chain as well.

    R8000 with the medium rear mech is designed for an 11-34 cassette. No issue at all with any touching of sprockets and jockey wheel.
  • milemuncher1milemuncher1 Posts: 1,472
    johngti wrote:
    Your top jockey wheel is too close to the sprockets on the cassette. Get yourself one of these.

    https://www.sigmasports.com/item/Wolf-T ... lsrc=aw.ds

    It moves the jockey wheels down and away from big sprockets in the cassettes. You may need a longer chain as well.

    R8000 with the medium rear mech is designed for an 11-34 cassette. No issue at all with any touching of sprockets and jockey wheel.

    You’re wrong.

    11-34 is pushing your luck with a medium cage derailleur. You at least need to increase the angle of dangle ( turn the b screw clockwise ).
  • webboowebboo Posts: 5,021
    johngti wrote:
    Your top jockey wheel is too close to the sprockets on the cassette. Get yourself one of these.

    https://www.sigmasports.com/item/Wolf-T ... lsrc=aw.ds

    It moves the jockey wheels down and away from big sprockets in the cassettes. You may need a longer chain as well.

    R8000 with the medium rear mech is designed for an 11-34 cassette. No issue at all with any touching of sprockets and jockey wheel.

    You’re wrong.

    11-34 is pushing your luck with a medium cage derailleur. You at least need to increase the angle of dangle ( turn the b screw clockwise ).
    Well what a surprise a quick google of a r8000 medium cage rear mech on Wiggle says it is compatible with a 11 to 34 cassette.
    God help the poor souls on your introductory rides with stuff you spout.
  • Vino'sGhostVino'sGhost Posts: 4,129
    Webboo wrote:
    johngti wrote:
    Your top jockey wheel is too close to the sprockets on the cassette. Get yourself one of these.

    https://www.sigmasports.com/item/Wolf-T ... lsrc=aw.ds

    It moves the jockey wheels down and away from big sprockets in the cassettes. You may need a longer chain as well.

    R8000 with the medium rear mech is designed for an 11-34 cassette. No issue at all with any touching of sprockets and jockey wheel.

    You’re wrong.

    11-34 is pushing your luck with a medium cage derailleur. You at least need to increase the angle of dangle ( turn the b screw clockwise ).
    Well what a surprise a quick google of a r8000 medium cage rear mech on Wiggle says it is compatible with a 11 to 34 cassette.
    God help the poor souls on your introductory rides with stuff you spout.

    Old school is good




    Honest
  • johngtijohngti Posts: 2,416
    johngti wrote:
    Your top jockey wheel is too close to the sprockets on the cassette. Get yourself one of these.

    https://www.sigmasports.com/item/Wolf-T ... lsrc=aw.ds

    It moves the jockey wheels down and away from big sprockets in the cassettes. You may need a longer chain as well.

    R8000 with the medium rear mech is designed for an 11-34 cassette. No issue at all with any touching of sprockets and jockey wheel.

    You’re wrong.

    11-34 is pushing your luck with a medium cage derailleur. You at least need to increase the angle of dangle ( turn the b screw clockwise ).

    Think you’ll find I’m not wrong but thanks for trying to help anyway
  • secretsqizzsecretsqizz Posts: 424
    Your top jockey wheel is too close to the sprockets on the cassette. Get yourself one of these.

    https://www.sigmasports.com/item/Wolf-T ... lsrc=aw.ds

    It moves the jockey wheels down and away from big sprockets in the cassettes. You may need a longer chain as well.

    MILEMUNCHER whatever version you are on seriously mate you need to censored right off this forum.. you are less useful than useless..
    this is almost serious advice fromm a c oc k womble like me.
    My pen won't write on the screen
  • rwooferrwoofer Posts: 202
    I have the same problem on the 14 tooth sprocket. The problem seems to be with the cassette, where one tooth has a slightly different shape. Very annoying that no amount of barrel adjuster (which I changed because the standard R8000 one is useless) will correct it.
  • johngtijohngti Posts: 2,416
    Had a poke around this evening. It appears that the problem was in two places on the 25 tooth cog. There wasn’t quite enough clearance for the chain to engage with the 27 without there being contact. Gave the 25-tooth a bit of a nudge outwards and the cable a bit of a tweak and the noise is gone for now at least.

    I wonder if there’s a difference in the thickness of the plates between the KMC 11-speed chain and a Shimano one. I suspect Shimano would probably blame the no -Shimano chain if I were to ask about it. I suspect that if/when the noise returns I’ll try a 5800 chain instead.
  • johngtijohngti Posts: 2,416
    For future reference, and to bring this thread to a full stop, the problem seems to be that the tolerances on the cassette are so tight that the gold coating on the kmc chain made it almost infinitesimally too wide so it would catch on two specific teeth but only when they lined up with the outer plates. At least that’s the only blooming explanation I can come up with because I’ve just fitted a 105 5800 chain and the problem seems to have magically disappeared!

    Anyway. Thanks for all of the ideas and help. It was much appreciated.
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