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Ultegra 6700 rear mech grabbing/seized

jordan_217jordan_217 Posts: 2,580
edited August 2013 in Workshop
My rear mech doesn't seem to be pivoting back/fore freely. So as I move up/down the cassette the mech isn't moving and taking up the slack on the chain. On the 28t sprocket the chain is near enough sandwiched between the sprocket and upper pulley, only manual intervention will move the cage to where it should be. The chain is grabbing and I'm sure I'm risking a severe mechanical....

I've tried a good spray of PTFE lube to free it up but I guess theres a lot of crud hiding in the area behind mounting bolt. I understand that I could overhaul this by removing the mech, removing the C clip and giving the tension spring and general area a good clean and re-lube. I've not tried this before - is it a straight forward job or am I opening a can of tension spring worms?

A rear mech is £52 so not too bad but I'd rather see if it could be sorted with a quick service.

Oh, and a short cage mech is fine for 28t isn't it? Just in case I do have to replace.

Any advice appreciated. Thanks in advance
“Training is like fighting with a gorilla. You don’t stop when you’re tired. You stop when the gorilla is tired.”


  • deswellerdesweller Posts: 5,271
    I have recovered Sora derailleurs in the past by immersing them in warm motor oil and agitating the pivots. It's amazing how much rubbish falls out, and using warm oil helps get it into the right places.

    Quite time consuming though.
    - - - - - - - - - -
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  • Monty DogMonty Dog Posts: 20,614
    Yes, remove the rear mech, dunk it in some cleaner and get to work with a toothbrush to remove up crud build-up inside the parallelogram, working all the pivots by band.
    Getting inside the sprung mounting pivot is no problem - the spring isn't that fierce and easy to wind-up for re-assembly.
    Make mine an Italian, with Campagnolo on the side..
  • rolf_frolf_f Posts: 16,015
    The high tech solution is to get an ultrasonic cleaner - less than £30 from Maplins. Great fun ultrasonically cleaning all sorts of things....!
    Faster than a tent.......
  • my ultegra rear mech was equally tardy in picking up slack in the chain - to the point that I had a nice thick black stripe across the chainstay.

    I took the mech off, gave it a good spraying of GT85, agitated all the pivot points etc. including some brushes to get into the awkward bits. Rinsed it all off (lots and lots of crud) and left to dry, relubed the pivots etc. and refitted and it worked perfectly again.
  • jordan_217jordan_217 Posts: 2,580
    Thanks for all the responses and tips. I'll strip it down and give it a good clean and re-lube over the w'end.

    Rolf, thanks for the heads up. I'll be visiting Maplins for that cleaner as my missus keeps pestering me to get her ring cleaned :shock: :lol:
    “Training is like fighting with a gorilla. You don’t stop when you’re tired. You stop when the gorilla is tired.”
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