Gears jumping about

ed1973

So my 2nd highest gear is slipping when pedalling, I had this before on another bike but fixed it with a new chain. So I put a brand new chain on and it’s still slipping. Then went for indexing the gears, but this did nothing. I have bought a new cassette so will try this when it arrives. What else could be the problem? I’m thinking:
Bent hanger
Bent derailleur
Bent frame

Am I missing anything else to try?

The Rookie

Usual cause is a worn cassette by a worn chain, replacing the chain often then makes it worse.

steve_sordy

Go for the simplest solution first before you start imagining bent frames.

You have fitted a new chain, and now have bought a new cassette. That should do the job.

If you change the chain before it gets too worn (maximum 0.75% stretched), then you should get three chains out of a cassette before you have to change the cassette. For the rings, look out for chain suck and also skipping or slipping like you are experiencing with the cassette.

ed1973

Thanks for the responses fingers crossed the new cassette sorts it

ed1973

Update.
New cassette combined with new chain has fixed the issue although there was a fair amount of fettling with indexing the gears but soon sorted it when I realised the terrible chain line I had in the highest gear. Switched the chain ring to the other side and all sorted.