I've got an old shimano BR-M555 rear disc brake and I'm thinking about swapping the 160mm for a larger one. The current shimano discs have a smaller braking surface so I don't think they'll work. Anybody know of a suitable disc I can use?

The ones i got with a Clarks upgrade kit seemed to work fine (203mm and 180mm)
Avid ones seem ok too. Hope will prob do the job also.
OR even the proper Shimano ones (RT61 i think)

Clarks upgrade kit – from where?
RT61 – only come in 160mm as far as I can determine

Teef, You can use any shimano rotor. CRC sell everything from 160-203mm, and the appropriate mount to get the caliper in the right place.

Any shimano rotor – not sure you can as the braking surface is smaller on the new rotors. So you'll end up with not all the pad being worn and I'm not sure this will work too well.

I used RT75 180mm shimano rotors quite happily until I switched to Hope floaters. No un-even brake wear.

Discs last ages. This issue does not concern me at all (and I use xt 203mm discs and 525s)

used RT75 180mm shimano rotors – with a BR-M555 brake?

04 Enduro expert came with M555s and 04 XT rotors which have a smaller braking surface.

5 years on they are still working perfectly. There is a small amount of fork juddering. No uneven pad wear.

Mine didn't have xt rotors. I'll have a root about in the shed and find the original ones tonight.
Whilst xt ones will fit, as the od of the discs is the same. The braking surface will be narrower. I dont suppose it'll be an issue tbh. But might as well make the most of the wider braking surface with the M555s. Good brakes I found.

Aye, didn't give it a moment's thought, should I have done? Mind you, this was a while back (2004/5) perhaps rotor sizes have changed?