Removing Stuck Brake Caliper Pistons

Jotally

Jotally

Hero member
Location
Coventry , UK
Over the years I have heard ( and tried ) various "remedies" for removing stuck brake pistons from calipers ranging from heat / use of a grease gun / compressed air  :o.

What method do you favour ?

Ally
 
Split the calipers, put your hand with a rag underneath over the piston to be removed and put a compressed air gun on the brake fluid port - POP and she's out in a jiffy.
 
Track pump (bicycle pump that looks like a stirrup water pump) and a plastic adapter to let you screw the hose into the inlet on the caliper. The one for inflating footballs works. Stick a thin bit of wood in between the pistons.

Whack the pistons back into the caliper before trying to remove them, in case they are proper seized, and stitch the caliper back together. The pistons almost never seize retracted, so there is always some movement, even if it's just a couple of mill.,

One piston still needed about 150PSI before it came out - with a huge bang!

If one side comes out and the other doesn't, use a small patch of inner tube to seal off the transfer passages between the sides when you bolt the caliper up, (or use a g clamp) and use the bleed hole to add pressure.
 
Sometimes air won't budge 'em and not everybody has a compressor. This might sound like butchery but trust me, it isn't.  Split the calliper and grip the protruding lip of the piston with a pair of molegrips. Get some heat into the calliper body with a blow torch and then put a large screwdriver/tyre lever through the molegrips at 90 degrees. Using the tyre lever as a errr...lever, you can then turn the piston and slowly withdraw. Works every time.
The lip of the piston is only there to push the pads, it doesn't go anywhere near the seals so any marks left by the grips are harmless. I've usually binned the old pistons in favour of Teflon coated alloy ones anyway so any damage is irrelevant.
 
If well and truely siezed, and they often are, a grease gun is the most efficient and safest, albeit messiest, method of removal. 

More often than not, seized brake systems won't work anyway, and you'll probably only be able to remove the loose pistons with the fluid still in the system if they do.  I've torn off more of those protruding lips than I care to remember, you sometimes reach a stage where none of it is left to grasp.  10bar (140psi) compressed air is sometimes not enough to budge the buggers, but when it does, don't point the piston at your face! :o  Heat sometimes helps, I've even resorted to completely burn out the rubber seal, piston then simply fell out!

Thankfully, only alloy replacement pistons generally available these days, won't gunge up as quickly as steel ones.

I've thought of omitting the dust seals, lets water and crap out without keeping it confined where it wreaks its havoc.  No Brembo 4-potters have dust seals on the pistons, probably a good reason for that...

piet
 
If you have steel pistons and access to a welder weld a bolt into the centre of the piston say M12 the heat from the welding transfers into the alloy body and you can grip the bolt in a vice and wind the piston out.
M.
 
The first thing to remember here is if you are about to work on your calipers and may need to part the body halves, then before you unbolt them from the fork legs, CRACK (loosen) THE CALIPER HALF BOLTS, much easier than trying to undo the bolts once you have removed them from the bike.The next thing is the bleed nipples, if they wont budge with a short spanner, just leave them for now, once you have snapped them off, you have a nightmare job trying to reclaim the threads, so dont snap them!

I am with Piet on this one, definately so,sometimes they just are so corroded in, air will not shift them,nor will heat and any kind of twisting and gripping,I have also immersed in boiling water to great effect, but sometimes all of that fails, so I no longer bother with any of them, I keep a modified banjo coupling, with a grease nippple ready to use a side lever grease gun and pump the piston out, with the caliper on the bench, as soon as one piston moves about 5mm, I then block it, so that the other one can move, ,this method has never failed me, and for the clutch slave cylinder, which is harder due to its siting, inside the cover, I  keep an angled nipple ready to screw straight into the hose conection, and again this has never failed me.

Not everyone has access to air or the grease method, and the best way without either of those is to use boiling water, split the caliper and drop the two halves in the water, for about 15 minutes, then remove (use tongs and gloves) pinch it up in your vice (to hold as though a asecond pair of hands) and use mechanical methods to twist (first) then lever out (second) plumbers adjustable pump grips will be best for twisting, and small pry bars the best for levering.

The next thing is the nipples, bung the caliper body back in the boiling water for another 10 minute stew, and then (tongs and gloves again) take the body quickly to you bench, and this time, pinch the  nipple in the vice, now try to twist the caliper body, if it moves at all, then work it back words and forwards, no more than 30/40 degrees untill it feels safe enough to unscrew it completely.

If this method fails you, all is not lost,find someone locally who can help you with the grease gun method.I would do that if you are anywhere near North Kent UK
CLEM
 
pushing the pistons in will sometimes free them up enough to get 'em out easier...sometimes is the key word...
 
Put 'em in my molasses mix, see GENERAL DISCUSIONS, no longer than 12 hours. You could piss into the ports to pushem out after that.

24 hours, and the aluminium will be attacked.

(How can spell check be smrta than me?)
 
Hi Ally, I've faced this many times over recent years and have tried all sorts of tricks, but the method that works best, most of the time, is to keep the caliper halves together and use the brakes on the bike to pump the pistons out (as Paul M and others have mentioned below).

The bike (or a mates bike) already has a ready-made pressure generator with all the correct fittings! With an assortment of levers/wood/clamps it is possible to hold back the piston that moves first and thus hold back the pressure for the stuck ones. I let silicon spray soak into the piston/seal for 24 hours before commencing attack.

Next best for me is compressed air, but be careful, things can happen quickly when a piston becomes free. Place thin wood sheet between this pistons to control what happens.

Once the pistons move, you can push them in and out a bit to get them free-ish (making sure to clean as you go). If they are not free-ish, then even the last few mm of engagement can be a bastard to get out by hand once you have split the calipers.

In my efforts - heat (torch/boil/whatever) has never helped.

Paul H
 
Calipers unused for 15+ years and most pistons frozen solid. 2 popped out with compressed air, the rest wouldn't budge in any direction. All came out after application of flame from the LPG gas gun, enough to soften the seal and then just pulled out with pliers.

1 x busted off nipple with broken off tip of easyout embedded removed by spark erosion at local engineers for $50 in 20min, thread is perfect.
 
Soak them overnight in diesel before using compressed air if they didn t budge just with air.

LJ
 
I just had great success removing rear postons with the grease gun. A good thing to try first because you cannot do damage.  Thanks for the tip.  Worked really well on the master too.
 
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