The bolt which holds the lower jockey wheel in on my XT mech has tighened itself whilst in use, this has pinched the frame of the mech together, seized the wheel and squashed the sealed bearings in the wheel which is now pretty useless. This is the second time this has happened, has this happened to anyone else? If so how did you cure it?

did the bearing seize first forcing the bolt to tighten? the mechs I have taken apart the bolt was shouldered anyway so could not overtighten and crush the bearing or there was sleeve

possibly not related, but when I unbolt a new jockey wheel they’re all loctited (or other subtance threadlocker), maybe you could try that. It’s never happened to me though.

Yup. Threadlocker is king. Don’t lean on them with threadlock though, or you’ll strip them when removing them…

There should be a central “core” a bit like a split pin (only thinner, sorry my word fu has dried up) which should stop the bolt overcompressing the bearing.

Thanks for the replies, yes there is a central core to the jockey wheel but it seems to have squeezed itself inside the holes of one of the outer plates allowing to jockey wheel to be squashed : (

As an update for anyone who is interested, I had another look at the jocky wheel last night and it the bearings were very tight again so I popped open the seals and stripped it down. Inside the grease had dried to a rock hard black gunk and seized the bearings, a good clean, some of rock ‘n’ rolls finest and its good to go again, at least till the teeth wear out!