Wobbly rear mech

[Ihatehills]

Hi all

I'm once again experiencing indexing issues, I've now replaced the cable and chain and cassete, and it does change correctly but not always smoothly. the strange thing is that it sometimes is hesitant to change up but other times it doesn't want to change down. I noticed when changing the chain that there is quite a bit of play on the rear mech mounting bolt is this normal? I'm thinking that this could be part of the problem

 

[Roadrider48]

Have you tried to tighten the rear mech bolt right up?

 

[lpretro1]

If the derailleur is snugly fitted and still has play then it is the main pivot getting worn - best to fit a new one

 

[Ihatehills]

Thanks for the replies, Yes the bolt is tightened fully. Its a shimano acera rear mech, do I have to replace like for like

 

[MPChurch]

If:
* mech is bolted firmly to frame
* bolt is not ceased preventing secure fitting
* Mech hanger is present and not damaged
then you probably need a new one.

New Acera rear mech; £23 from Halfords, £16 on eBay. Try you local cycle shop.
Don't if a Tourney (Halfords £12) would work, but others may be able to advise. Altus would probably work (£20).