My wife’s been using her road bike for commuting so it’s taking rather a lot of winter road abuse. The rear mech has stopped rotating properly forwards/backwards meaning that the jockey wheel ends up miles away from the cassette or she gets really slack chains. PITA.

Have tried some no-brand penetrating lube and some Muc-Off Bike spray to loosen (along with lots of wiggling) but it’s still really sluggish.

Any other suggestions for getting this to move properly? Could the bolt that it rotates around be worn and need replacing?

More likely to be clogged with road grime. The pivot bolt can be removed (circlip on the back)to give access to clean and regrease it, a bit of a fiddle to put back together, i’d recommend an allen key clamped in a vice, and a friend to slide the circlip in while you hold it all together.

What coatesy said! Dismantle, clean thoroughly, grease, reassemble, joy! The spring that holds the mech against the chain will try and fly off so cover the whole lot with a rag when you dismantle (DAMHIK)there’s a plastic bush/washer you’ll need to retain and clean in there as well.

Thanks for the tips. Will iron my ‘patient’ trousers for the reassembly task.