SLX 12sp slipping

I have 12sp mostly SLX on my ebike. Recently replaced cassette and chain, aligned hanger, was working fine.

Had been using a KMC chain, which was a bit noisy, but seemed to work fine. Started slipping in the highest gear (10t) under load.

Assuming the KMC chain might be causing excessive wear, have swapped to a new SLX chain and new 10t cog – still slips under load.

Lockring is cranked up as tight as I’d like to go, I’m assuming the hanger alignment is still ok, as all the other gears perform fine – they are temperamental when it’s not aligned.

Any ideas?

TIA

Any ideas?

Worn chainring – check to see if it is ‘grabbing’ the chain at the 8 o’clock position as you turn the cranks.

Chainring worn?

FWIW I always replace the chainring when the cassette is replaced.

Also, why is there “load” in the 10t cog…

Worth checking the B tension to make sure you’re getting as much engagement with the 10t as poss while still shifting OK at the other end of the cassette.

Also, why is there “load” in the 10t cog…

When I say load – pushing hard on the cranks even on the flat

Worth checking the B tension

I did set it up with the mark on the cage to align with the largest cog, but will check again.

Chainring doesn’t look bad, but will consider it as a possible cause

Actually rather than just the B screw check the whole mech setup – if the limit screw is off that could cause issues too. And how old are the inner & outer cable?

And how old are the inner & outer cable?

Around a year for the inner, but the outer is old

I did set it up with the mark on the cage to align with the largest cog, but will check again.

Had lots of trouble with this mech too on my son’s bike.

Somewhere I read to not set it up to the cage line and you might get better shifting. I think the recommendation was to have a bigger gap.

Check the alignment of the 10T cog, it’s quite easy to tighten a 12speed SLX up with all the cogs aligned whilst having the 10T misaligned slightly. If the 10speed is not bang on flush it will make a clicking noise and start slipping.