It pushed back in ok – do i need to panic about anything or just give them a good bleed through?

That'll teach me to faff with the sticky pistons – one pump too many!

Unlikely that you'll have damaged anything, clean up the fluid, bleed them through and check for leaks under pressure, after all, essentially all you've done is what you'd do when servicing the caliper.

They'll be fine but expect them to be a pain to bleed. Just run through the normal procedure but it'll take longer than normal to get all the air out.

as above, probably no problem – do a slow bleed making sure to tap the calliper / lines to make sure all the air comes out

ta. was meddling to try to free the pistons, but they do seem to play up in the cold. Anyone else had this problem?

It always seems to be the left brake(rear) which sticks. It also seems to fade and pump up. I realise this indicates air but they are a nightmare to bleed!

I know others with the same problem on the rear.

Just don't damage it you can buy everything as a spare other than the piston 🙁

odd. mine was sticking on the left too. i caught the piston as it came out so its all ok.

It always seems to be the left brake(rear) which sticks. It also seems to fade and pump up. I realise this indicates air

Yeah, if you have air in the caliper, you should expect it to stick; when you release the leaver, the air bubble will expand instead of the piston withdrawing.

but they are a nightmare to bleed!

Shimano breaks are trivial to bleed, it's a 15min job even if you start with no fluid at all, just follow the manufacturer procedure.

odd. mine was sticking on the left too.

IIRC, in Shimano brakes the pistons are different size to improve modulation, so you should expect the smaller piston to start sticking first, as the force moving it is smaller.

I partially popped the piston out of my front LX caliper (it didn't drop from the caliper but I lost all the fluid). With some input from the folks here I just pushed it back in, refilled and rebled the system (for the first time ever) and everything's worked fine since.

Interestingly I shop mechanic told me that it'd need rebuilding with new seals but the people on Singletrack reckoned it'd be fine and that seems to have been the case.