Servicing my brothers old C2. Got the semi-seized piston out of one sized but the other is stuck fast. Left it to soak in GT85 which I'm hoping will do the trick but if that fails, how? Don't mind killing it as I've got a new piston to drop in.

Hammer / screwdriver / monkey wrench time?

You've tried using circlip pliers presumably ?

Nope. Tried using a pin spanner, shoving it in the holes in the piston and trying to turn it to free it. No luck…

More leverage then 🙂

Or try some heat shock – boiling water on the piston with caliper wrapped in wet, cold rag etc.

trackpump 8)

>trackpump

C2 pistons are screwed in to the caliper 🙂

aaah forgetting myself, been a few years since I sold my C2s…
seem to remember it was one of the magic ways for removing stuck pistons, just got the wrong brake 😳

Actually the recommended removal technique does involve a trackpump – unscrew first then use trackpump to pop piston out.

"4. Closed 2 caliper
The piston requires unscrewing using a pin spanner. In most situations the piston
will easily unscrew, if it is tight then do not force it with the pin spanner or you may
damage the piston, in this case use the appropriate Hope tool available from your
Hope dealer. Unscrew the piston to the end of its travel, at this point it will rotate
freely without unscrewing any further. Now follow step 5 to completely remove the
piston from the caliper.
XC4 Caliper
The procedure is similar to the Closed 2 caliper described above except the piston
requires unscrewing using a broad flat blade.
5. To remove the piston (all calipers) a bicycle ‘track pump’ is required. Open the
bleed nipple 1/2 turn place the air line over the bleed nipple. Place your thumb over
the recessed transfer hole and ask a second person to apply pressure with the
pump. The piston will eventually eject with some force so point the caliper towards a
clean rag to catch the piston and prevent damaging it. Caution : do not look directly
at the piston whilst carrying out this operation otherwise it can fly out and strike you
in the face."

There may be something helpful on the Hope Website ??

page 12/13 may help??

Think I've got it. Piston is rotating (slightly) but can't seem to undo it. Going to have another look now… assume it just unscrews left-loosey!

More help! Got it so the piston rotates slightly now but it won't unscrew. Keeps springing back into the same position. Won't pull out either (or doesn't seem to want to).

Anymore ideas before I contact Hope?

Having the proper tool and a vice to hold the caliper steady helps a lot. I've been in this situation many times with neglected brakes, a dribble of GT85 around the piston edge to lube the sticky seal also works wonders.