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Transmission Clunking when Power Increases

desdeadlydesdeadly Posts: 48
edited February 2010 in Workshop

I have a look 585 with SRAM Force.
When it is on the big chainring on the front (it doesnt matter on the back) and i apply force to the pedals it clunks, kind of sounds like something is slipping.
At low torque its ok

Thinking it was the freehub i swapped to my other set of wheels (which i know are ok) and the problem persists.

I have had a look and i cant see anything obvious.
Any ideas?
currently the groupset has done around 600 miles i would guess.



  • LigLig Posts: 178

    Sounds like bottom bracket cups. I have had this often. you just have to strip down regrease and rebuild.....

    Try it if no one else comes up with an easier solution to try first..

  • Ben6899Ben6899 Posts: 9,686
    What does it feel like when the clunk happens?

    Bikes: Donhou DSS4 Custom | Condor Italia RC | Gios Megalite | Dolan Preffisio | Giant Bowery '76
  • Cheers Lig

    Ben - it feels like the chain (or something) is slipping. Perhaps not quite coming off as there seems to be a bit of resistance. It makes an awful sound also. Again like metal slipping/missing/skipping on metal. its quite loud.
  • ClemClem Posts: 546
    I have the same problem. I suspect it's not having your indexing setup absolutely perfectly.

    When my Airborne was a Campag 9 speed, seven years ago, I took it for a once-over at a bike shop and they said I'd done a pretty good job on setting up the transmission. Sadly when I swapped to 10-speed I clearly didn't get it right... I get the feeling 10 is a lot more fussy than 9. I get one end of the range to work fine at the back and the other isn't happy and vice versa. Get the middle wrong and it clonks away on climbs and the levers need 'nursing' to shift the gears up or down.

    One day I'll strip the whole thing down and start again!
  • balthazarbalthazar Posts: 1,565
    Consider loose chainring bolts also. Often forgotten.
  • ClemClem Posts: 546
    Very tight on mint condition chainset... I'm going to change my levers and cables next. Can't do any harm and I have spare levers.
  • Ben6899Ben6899 Posts: 9,686
    Check the chainring bolts for tightness for sure, as someone mentioned upthread.

    If the indexing isn't quite right, then could that cause the chain to ride on top of the sprocket teeth on the cassette?

    Bikes: Donhou DSS4 Custom | Condor Italia RC | Gios Megalite | Dolan Preffisio | Giant Bowery '76
  • ClemClem Posts: 546
    Well Ben, it must be something like that. If not riding on top then going to the 'wrong' place on the sprocket.

    What baffles me is why some cogs should work fine and others not... perhaps there are chain issues but I've used Campagnolo and two other makes with pretty much same results.
  • Checked chainring bolts, striped down the BB last night, cleaned and regreased. put back together and still the same.
    Then I noticed the chainrings themselves, i think i overlooked the obvious, DOH ... =516143907
  • ClemClem Posts: 546
    My problem's at the other end and all my cogs are in good nick but I hope that solves your problem.
  • markos1963markos1963 Posts: 3,724
    I see nobody has mentioned pedals yet. Could be the bearings on them if all the other areas have been tried.
  • ClemClem Posts: 546
    It certainly isn't the pedals in my case. Changed them with no improvement (I didn't do this to see if there would be an improvement if the chain does run cleanly at the rear sprockets wouldn't seem to be down to pedals)...
  • keef66keef66 Posts: 13,123
    Nice pic! I'd say your chainring's reached the end of it's useful life :( and is almost certainly responsible for the phenomenon you describe.

    You certain you've done that to it in 600 miles? I'd have a good look at the cassette and check the chain for wear while you're at it.
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