Rear derailler touching cassette after ride

twhicher
twhicher Posts: 3
edited February 2013 in Workshop
Looks I've busted my rear derailleur:

I was out for a ride yesterday, enjoying the awesome weather and while shifting under load (should have planned better), my rear derailleur locked up. I got off the bike, shifted back it cleared and seemed fine.

Started riding again - the bike didn't feel quite right and was noisy from the rear cassette, but still rode and gears were shifting. On inspection the rear derailleur jockey wheel is now touching the cassette (in all gears). I've tried adjusting the b-screw (which was almost all the way out so plenty of movement), but it doesn't seem to be having an effect.

It looks like the derailleur isn't springing back against the stop (hence the b-screw doesn't make a difference), but I can't see anything obviously missing or loose. The mechanism still has some 'spring' to it.

Anyone got any thoughts on whether that diagnosis sounds right, and if so how I repair her! With nothing to compare too its hard to know what 'right' looks like. Cheers!

Comments

  • Monty Dog
    Monty Dog Posts: 20,614
    Firstly, check rear mech alignment - the jockey wheel cage should be vertical when viewed from the back - any excess force can bend it out of position. The spring inside the mounting boss on the rear mech can get gummed up or broken. Remove chain, cable and unscrew the rear mech from the frame. Carefully release the c-clip that holds the mounting boss in place - making sure the clip doesn't fly-off and get lost. The mounting boss should pop-off and you can remove the spring for cleaning. Relube and reassemble - making sure you wind the spring as you fit the boss and refit the c-clip to secure
    Make mine an Italian, with Campagnolo on the side..
  • smoggysteve
    smoggysteve Posts: 2,909
    Could you take a pic of it so we can get a better idea of what you mean?
  • Thanks for the help Monty. I took it apart and gave it a good clean. The spring seems fine so I put it back together hoping the problem would be solved. Felt like there was plenty of power in the spring when I was reassembling. However, no such luck.

    Two pictures showing the problem - first one, jockey wheel touching the rear cassette. The second shows the derailler appearing not to have enough spring to pull back against the chain tension.

    Any ideas? I don't want to buy a new derailler if it can be fixed, or worse there is something else causing the problem..

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  • smidsy
    smidsy Posts: 5,273
    It's upside down.
    Yellow is the new Black.
  • keef66
    keef66 Posts: 13,123
    Take it off again. Is there a stop on the hanger against which the mech should be located? That should stop it rotating too far forwards. (Made this mistake on one of the kids MTBs once)