my lbs has got my hope m4 brake in for a service and they told me one piston is stuck altho it moves it wont come out. he tried using compressed air to blow it out but no joy. he is going to try compressed air with the other pistons in and held down this eve

if this doesnt free it any other tips he might try.

thanks

If it's in your lbs why don't they phone the very helpful guys at hope?

he said hes gonna try again tonight then call but thoght someone here might know something useful

Ive used isopropyl alcohol to free stuck and sticky pistons before with a cotton bud or syringe.
hopes can be a bitch tho

My mono m4's are going to the shop for new piston seals and a good strip down and service as they've started sticking on which gets quite annoying when your tired! Hopefully i don't have the same problems. Hope they manage to sort yours for you.

An air compressor is what you need to get it to move!

Put the other pistons back in, use a block of wood to jam two of them. Then use a tyre lever to hold one while you press the troublesome one out with compressed air or, if needs be, with the brake bled again.

cheers chaps will chat to lbs tomorrow

It'll only move if they do it with the other pistons in, otherwise it's got some very big leaks 😉 Using a decent pressure they'll shif pretty much anything, though they want o wrap it in a rag save having a projectile.

I would go along with what 3 fish said. That is re-assemble it re bleed it. You can compress air but not a liquid so if you block the 3 free pistons the 4th sticky one should move. Additionally you could warm the calliper up with a hair dryer or pour a kettle of boiling water over it. The alluminium calliper will expander more than the piston, this should help free it, while pumping it.

Bit of wood to block 2 and ziptie the 3rd?