Chain slipping on cassette

steelo

I have just replaced my cassette with a shiny new SRAM PG990 9 speed and the chain with a SRAM PC991 9 speed. I have an XT Shadow rear mech. I have made no adjustment to the rear mech after swapping out the cassette and chain. In certain gears the chain is derailing and slipping up/down 1 gear. I would have thought that a straight swap of chain and cassette would cause no issues. Am I wrong? Do I need to take the chain off and realign the derailleur with the cassette as though I was fitting it new?

Cheers all.

cooldad

You need to reindex the mech.

TJ20862

basically adjusting the cable tension

drlodge

The rear derailleur shouldn't need adjusting if you just change the cassette like-for-lie, but it sounds like it does. Did you make sure any spacers were also put back like before?

cooldad

Where do you see like for like?
And if it doesn't work it needs indexing.
Quite simple.

cooldad

TJ20862 wrote:

basically adjusting the cable tension

Maybe. But it is also likely that the cogs are in a slightly different position, so check limit screws and index properly. It take a few minutes.