Should I change my chain?

[Panter]

I replaced my cassette and chain a couple of months ago as the chain had worn to 0.75 (or whatever it is on the chaintool checker.)

The indexing was never quite right, and it would skip occasionally despite my keep adjusting it.
I finally got it in the workstand yesterday for a thorough clean, new cable and to sort the adjusting out perfectly, which is when I discovered the cassette is warped.
When you spin it, some of the chainrings oscillate, as if it were a buckled wheel, hence my shifing problems.

So, I've ordered a new cassette, but I'm wondering if running a ropey cassette will have damaged the new chain. Should I replace that too?

If it matters, groupset is Tiagra/Sora (8sp) chain was SRAM 8sp and the cassette was also an 8sp SRAM (PG820 IIRC?)
The new cassette will be a SRAM PG850.

Any advice appreciated

 

[fossyant]

Just check it's not the freehub...some do oscillate a little on the lower end ones, but certainly relpace the cassette first. Chain should be OK.

 

[Panter]

Thanks Fossyant, it's not the freehub, and most of the rings on the cassette are Ok it's just three in the middle.

I wonder if it's just a faulty cassette?

I won't order a new chain then (phew )

 

[Tynan]

don't some of the cassette's have some of the rings made a bit irregular to improve shifting?

 

[Panter]

I think so, but this one is so wonky that its snagging the chain and constantly causing it to do "half-shifts."