Brake caliper piston removal...
 

I'm going to rebuild my front brakes, but it seems I'm having a difficult time getting the pistons out.

What are my options as far as getting them out without damaging them? The upper ring on the piston, I'm sure I can use some tape and then some vice grips on it; but if that upper ring gets scarred, does it matter all that much if it's on the sides and not the top (where it meets the shims)?

Any other tips would be helpful. The air compressor only blew 1 of the pistons out. One of them came out easy, the other 2 are being a pain (and I'm rebuilding both sides, just working on one until I know what I'm doing so I don't break both).

if you have access 2 a hydraulic press you can place the other piston back in (just so its air tight) then place the press on this piston 2 hold it in place while you pressurize the caliper
with an air hose then begin 2 slowly press down on the piston. this has worked 4 me before (it was only a 2 piston caliper though) its worth a shot.

Mahjik, here's how I did it: Take a small block of wood to insert between the four pistons, so that they can only move out so far before stopping. You want to make the block thick enough that no one piston can move past its seal. That keeps the pressure in the caliper, and (for me anyway) all four popped out enough that I could remove the air and pluck out each piston by hand. They didn't all pop out at the same time, but eventually each one did.

If you have one that sticks, you can use shims on the block to allow that one piston room to move while the other three are held in place.

This is easier to do than describe. My block of wood was actually a mix of several pieces of scrap (a couple of paint stirrers and an old dowel rod), and I layered them in combination to position the piston "stop" where I needed it. The inner walls of the caliper body have nice flat surfaces against which the wood can be braced.

I really don't think that you want or need to use a press to put the pistons back in. The caliper should be under no pressure when installing the new seals and pistons.

Never done it myself bit I've always been told to use compressed air to push them out. I have no idea how much pressure it will take.

Thanks guys.

artowar, that was my thought after seeing only one of them pop out. Unfortunately, I'm just lame enough not to have my own air compressor (I borrow a local forum member's when I need to use one). It's on my list, I swear! :)

I go ticked off at the two pistons being stuck on there and found a tool that should help:

http://www.hrpworld.com/index.cfm?fo...action=product

I placed an order last night. I'll let everyone know if the tool works or if I got back with the compressed air solution.

Thanks again for the help.

^
ooooooooooooo!! Those are cool! I want one ;)

I'll let you know if they work. ;)

Actually, I don't have one either. But I do have a nitrogen tank that I bought to charge my shocks. I ended up using it to fill my tires and misc. stuff around the house. Came in handy to blow out those pistons too.

That tool looks handy for straightening out a cockeyed piston. If it's aluminum you should have little risk of scratching the pistons with it.

I hope so. The tools should be here in 2 days.

BTW, what about that upper ring (above where the rubber seal sits) on the piston? I did scrape it a little on the side, but not on the top that meets the brake pad shims. That part doesn't seat into caliper itself, so I'm thinking it shouldn't matter too much but I do plan to sand it down when it get the piston out.

I think that as long as the seal groove is clean and undamaged, and the piston top (that meets the shims) is clean and undamaged, it should be fine. Maybe sand off the crud and leave it at that.

I've been thinking about having the inside of the piston "cup" media blasted, then coated with some type of heat barrier coating. I just have to get around to checking how much it will cost...

Hey guys, the tools showed up today. I had ordered the 1.250" and the 1.375".

The smaller is what I measured for the upper ring, the larger is what I measured for the lower piston area.

Either my measurements are off (which is quite possible) or the tools are just made to be that tight. I was able to use the 1.250" wrench and grab onto the upper ring of the piston, then work it loose. So, the tools do work.

However, if you can use the "block of wood" trick, that would probably be much easier.

Thanks for the help guys. ;)

kyle you are a man among men :)

Naw, I'm just trying to get my car back on the track. It's not a fun feeling loading up your car at 5AM for the track weekend only to back out of the garage with no brakes. sigh.... Thankfully, it was a cheap track session so I didn't lose that much money. ;)

Reviving this thread to link to AP's how-to page:

http://apracing.com/roadcar/caliper/calservice1.htm

Good info in the link.

Someone should make and sell that little insert for FD calipers. ;)

If you don't have an air compressor you can also temporarily hook the caliper back up to the brake line and use the pedal to slowly push them most of the way out. Just don't go too far or you'll have a real mess to clean up :D

vice grips then use a screwdriver as a wedge to force the vicvegrips away from the caliper, brigning the piston with them. slow and steady, cautiously avoiding damage to the piston ends.

good luck man

Here I am, another person doing without compressed air.

Is the brake rotor itself a suitable clamp block? It would seem that if I removed the pads then pressed the pistons onto the rotor that I might have the pistons very easily accessible.

Dave

Clamping the caliper pistons onto the bare rotor worked nicely.

Dave

Just curious about the rear brake calipers since they have to be twisted to turn them in how would u go about putting new pistons in by hand? Do you still need to twist?

wow that looks interesting. What size to order for FD?