Brake calliper problem.

[AlanAce1967]

I knew i had a seized piston on my left hand calliper as the pads were wearing out of shape, i carefully used a pair of small g clamps to wind back and hold the right hand side pair of pistons of the left (sitting on bike) calliper, i then sprayed WD40 onto the stuck pistons and pumped the brake, left for a while and repeated until both pistons had pushed themselves out approx 10mm, thought i had cracked it, went to push them both back so i could repeat and then clean them and neither will go back, all the other pistons on both callipers will go in and out with no problem but these two are refusing to move. I have some wood against the calliper so not to damage it and am tightening the g clamps as much as i dare but they won't budge. I also tried removing the fluid lid, still no go. What have i done, what do i need to do ? The bike is an 03 plate, ABS version near Peterborough, i can't afford main dealer prices ! Any ideas/suggestions gratefully received.

Alan

 

[Black Rooster]

wd 40 can make the rubber seals enlarge (should use brake disk cleaner)


u might have to pop them out clean the corrosion out of the seal seat with a wee pick ( soak the old seals in dot 4

might help

 

[mikeyboy]

AS ABOVE
WD40 is a big no no.
i would refurb the caliper,the repair kit comes with new pistons.@£70 per caliper.
if you dont fancy doing it, i can do it for you no prob.
feel free to PM for more info
mike

 

[monkeyboy]

The kits are ridiculously expensive for what they are. The pistons are plastic aren't they?

Personally I would carefully try to rotate the pistons with some grips to try and break whatever seal is stopping them going back. You could also try loosing the brake line bolt at the caliper when you're winding back. If the pressure isn't absolutely square to the piston they can wedge easily. Might be a bit counter intuitive at this point but just push them out a bit further before trying to push them back. If you have room, you could try putting the pad over the two pistons and clamp them back together.

 

[Steptoe]

Pointless removing the fluid lid if you have servo/abs brakes

 

[AlanAce1967]

Pointless removing the fluid lid if you have servo/abs brakes

Tell me what to do Mr Steptoe ! Please !

 

[AlanAce1967]

I have abs issues anyway and was considering an abs/servo removal, any one want to quote ?

 

[AlanAce1967]

Can anyone recommend anyone in the Peterborough area to do the job ?

 

[Deleted account 190117001]

Do not put any sort of grips on the pistons, that will totally fuck the pistons up.

 

[monkeyboy]

Do not put any sort of grips on the pistons, that will totally fuck the pistons up.

That totally depends on the grips. If they are big enough and can push the piston in straight there's no problem IMO. If you just get a grip on the edge and push then they will certainly wedge themselves. If I'm gripping them laterally to turn the piston then I'll put some cloth between the jaws to protect the piston. I've got some of these

but they're not 100% and don't suit all piston sizes. I'll agree you do have to be very careful with grip though

 

[Deleted account 190117001]

That totally depends on the grips. If they are big enough and can push the piston in straight there's no problem IMO. If you just get a grip on the edge and push then they will certainly wedge themselves. If I'm gripping them laterally to turn the piston then I'll put some cloth between the jaws to protect the piston. I've got some of these

but they're not 100% and don't suit all piston sizes. I'll agree you do have to be very careful with grip though

Yep I see what you mean now.
However the OP seems to not have any knowledge about brakes/ callipers and pistons, so any advice needs to reflect this, we don't want them to fuck something up on our advice. ( vice ! , geddit ? )
My honest advice to the OP whom appears to have little or no experience would be to get a professional to work on their braking system.
It's not something to be tinkered/ tampered with.

If he's feeling up to it though and has lots of time and patience, one hour searching on this site shows lots of posts/ photo's of this particular job.