SmudgerEBT
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| posted on 15/7/16 at 07:33 AM |
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Brake Calipers - Removing Pistons
Ok, so got some calipers that I want to strip down and fit new pistons to.
They are metro 4 pot.
How can I remove the pistons without access to air (to force the pistons out), can I just split the caliper and use a tool of some sort to remove or
do I need to force out the piston using air or some sort of hydraulic system?
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micksalt
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| posted on 15/7/16 at 07:50 AM |
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Chances are that any attempt to pull the cylinders out will result in damage to the bores. In the absence of compressed air, do you have a master
cylinder and a spare interconnecting pipe handy? It would be a bit messy, but if you assembled and filled with brake fluid, you could use that to
eject the cylinder.
Personally, I would say where you are in the world and see if a fellow Locostbuilder is nearby with an air supply. Don't forget to stick a piece
of wood between the cylinders to give them something soft to fire out against.
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nick205
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| posted on 15/7/16 at 07:55 AM |
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Assume they're front calipers and not rear ones with wind in/out pistons?
Granted you should use a wind in/out tool to spin them out, but the tools are quite cheap and I've done it before with an adjustable spanner and
some care.
If you need air to blow them out then a friendly garage or engineering company may well help you - turn up with some cake or bicuits and you may get a
favour done.
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Camber Dave
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| posted on 15/7/16 at 08:03 AM |
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To remove pistons on a pair of HiSpecs, I made a bar 2mm bigger than the inside of the piston then tapped a fine thread right through it
I sawed a pair of slots at 90 deg in one end and then squeezed them closed.
I put it back in the lathe and finished it to a tight fit in the piston
Then when the screw was tightened it jammed the tool in the piston and by turning the assembly the pistons came out with out a mark on the working
surface.
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Slimy38
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| posted on 15/7/16 at 08:09 AM |
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I have had some success with reverse pliers inside the piston, although the pistons were in fairly good condition and moved quite easily. I
don't know if it would be similarly effective with stuck pistons, and while I couldn't see any bore damage it doesn't mean there
wasn't any.
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SmudgerEBT
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| posted on 15/7/16 at 08:33 AM |
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They are heavily rusted (hence free) so might just drop them into some Bilt Hamber first, before trying to split them.
Will take them to local garage and have an ask, they can only say no haha
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AlexXtreme
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| posted on 15/7/16 at 08:41 AM |
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I brought a cheap tyre electric pump and this worked very well (only cost £8!)
Alex
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SmudgerEBT
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| posted on 15/7/16 at 08:58 AM |
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Didnt think that would have enough pressure.
Once split will give that a go.
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Slimy38
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| posted on 15/7/16 at 09:56 AM |
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quote:
Originally posted by SmudgerEBT
Didnt think that would have enough pressure.
Once split will give that a go.
As long as it's airtight it should eventually get them moving, although it could take a while to build up. I have an electric pump for car
tyres, it takes a good fifteen minutes of running to get the tyres up to 30psi, but it does get there.
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AlexXtreme
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| posted on 15/7/16 at 10:02 AM |
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Watch out when they come out if they are really stuck - they can do some damage! Definitely where some safety protection (dont normally bother but in
this case I have). Heard of someone who broke their windscreen when they came out....
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tegwin
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| posted on 15/7/16 at 10:21 AM |
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Dont split them... Use a grease gun on the inlet with the bleed nipple closed... the pressure from the gun should be enough to push the pistons
out...one will move first, dont let it pop out but wedge it still so the other has a chance to move... A lot less explosive than using compressed
air.
If they are refusing to move under pressure give the caliper body a good smack behind the piston to shock them into moving.
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joneh
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| posted on 15/7/16 at 11:38 AM |
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I gave mine a tap with a hammer to free them and squeeze them in a bit, then used a tyre inflator to pop them out.
Stick a bit of wood in the middle and ffs don't put your hand near it when they're pressurised!!!
If they're twin pot you need to then put one back in and hold it with a clamp to get the other to pop. I wouldn't split the caliper
personally.
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SmudgerEBT
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| posted on 15/7/16 at 12:11 PM |
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Thanks for all the advice.
Won't split.
Will do it once been in the Bilt Hamber rust remover for a while (fingers crossed that will make removing things easier).
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gremlin1234
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| posted on 15/7/16 at 01:15 PM |
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quote:
Originally posted by AlexXtreme
Watch out when they come out if they are really stuck - they can do some damage! Definitely where some safety protection (dont normally bother but in
this case I have). Heard of someone who broke their windscreen when they came out....
include ear defenders in that too- they come out with a
Bang.
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gremlin1234
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| posted on 15/7/16 at 01:19 PM |
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quote:
Originally posted by micksalt
Chances are that any attempt to pull the cylinders out will result in damage to the bores. In the absence of compressed air, do you have a master
cylinder and a spare interconnecting pipe handy? It would be a bit messy, but if you assembled and filled with brake fluid, you could use that to
eject the cylinder.
I once did it with an old m/c, and used water, a lot less messy, and everything was getting new seals etc
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Ian.C
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| posted on 15/7/16 at 07:10 PM |
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I recently had the same issue with some Cosworth 4 pots, someone had had a go previously to get them out and even 120 psi couldnt get them out, I
eventually got them out drilling and tapping the centre of the piston and pulled them out... it was only a bit of gum that was preventing them coming
out, I knew I had to replace the pistons in any case. I used Bigg red for the replacements. Obviously I had to split the calipers.
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hearbear
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| posted on 15/7/16 at 11:49 PM |
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quote:
Originally posted by tegwin
Dont split them... Use a grease gun on the inlet with the bleed nipple closed... the pressure from the gun should be enough to push the pistons
out...one will move first, dont let it pop out but wedge it still so the other has a chance to move... A lot less explosive than using compressed
air.
If they are refusing to move under pressure give the caliper body a good smack behind the piston to shock them into moving.
+1
I did this with escort calipers and worked well and very controllable as he said just jam the 1st one to move before it comes out to allow the
pressure to work out the other one.
3.9Ltr SSC Stylus should be fun
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