Freeing stuck brake pistons with basic tools and no mess!

[andy120t]

I've been struggling with extracting 6-pot pistons from my ZX6-r (which has sat through lockdown and beyond and slowly seized up,) and I've been slowly trying to fix. They were stuck solid..all 12 of the little blighters.

I've seen various other tips but haven't found them easy in my garage and with limited tools;
- grease...I've only got a tiny grease pump and it didn't seem to get any pressure going. Plus it's putting lots of muck in the caliper.
- compressed air ...attaching a line always seems tricky. I've used this before on a garage forecourt but never felt it seemed very safe. Plus, with these caliper body shapes it's been quite hard to hold or fix anything to ensure one didn't pop out too far and still leave the rest.

So I found this clip online (and from Yorkshire!) and it certainly works. I split my calipers first so I could get to three pistons at a time. Jam the inside of the piston with screwdriver bits ( or small sockets) and a large allen key which you'll use to turn it. Once you start turning and it all jams up the piston will start turning. Then twist it upwards and it will slowly wind out. Amazing! And no mess.

I tried it a few weeks ago and managed to get them all turning but they were still not keen to come out.So I sprayed a lot of wd40 around the pistons and forgot about them until today. Today they just twisted out relatively easily. Genius!

https://youtu.be/HZ1SLCHR8EI?si=qUrjdM7dwXy6Itv9

[McCabe-Thiele (Ted)]

Looks like an honest video as it did not work within a few seconds.

Are they normal caliper pistons or like some automotive ones where you have to use a rotary retractor to push the piston back normaly?

[Laverda Dave]

Those workmate jaws were straining as much as he was! Good method though and there was no 'here's one I prepared earlier' staging going on. I don't think wet and dry will remove that scuffing on the piston either, that's a bin job

[andy120t]

Mine are just normal pistons, so nothing unusual. They were pretty solid so the first time I just managed to get a couple of them loose and turning after about 45 mins. Then I got fed up, sprayed them with wd40 and left them for a few weeks. I think the wd40 certainly helped - today they were still tight and I had to clamp them in the vice and put a lot of effort in, but the method definitely gives a solid grip on the inside of the piston, so let's you grip it and turn it.

Every now and then, or if something slips then the whole lot 'explodes' everywhere but if they are jammed in you can feel if it's right and gripping.

Very satisfying today when it all worked and they all came out!

[DomP]

I used a method an old American bloke uses on his XS650 on YouTube, same principal but using a large nut and bolt wound out inside the piston, stick an open ended spanner over the bolt then a bar through the ring end to twist while pulling up gradually.  Photos might help with this description 😀

[Bryanj]

In a situation like that i would not remove the caliper from the hose but only from the fork, remove pads and put a flat tyre lever in the middle then pump out the pistons with the lever

[K2-K6]

Some good alternative methods there.

I'm similar in trying to first pump them out with mastercylinder pressure if possible. 

In MTB brakes they have more currently moved to "bleed blocks" that are more or less as described with a tyre lever or similar to put between the piston to lever them out by holding some in.
More specifically they are used in place of pads for bleeding the caliper when off installation to then leave a bled system with space to fit a new set of pads during installation.  Usually they're just plastic blocks and maybe supplied with a new caliper to facilitate this and being of correct shape to fit.

People are 3D printing them though with say one piston space deleted so that you can focus on one stuck piston individually, while any others are held bake in their bore.

I'm up into the hundreds of these in freeing them up ftom corrosion around that piston seal (they ate similar to our Honda arrangement for that aspect) so many not maintained or excessively jet washed to their detriment. 

[AshimotoK0]

Looks like a great idea .. I will have to try it.

On the CB250RS I have just got, it came with a spare caliper but somebody had drilled and tapped the alloy housing to force the piston out and then fitted a short allen screw in order to seal up again (no sealing washer fitted  either) . Ugly looking bodge though IMHO. I have drilled and tapped the piston before, when I knew the piston was knackered (as they usually are). I have never tried the grease gun method but piped up to a master cylinder and used the hydraulic pressure to remove the piston. This is what I did on the seized but unmolested CB250RS caliper that was fitted to the bike.

[Johnny4428]

Liked this video, mainly because it’s what we do the whole time without realising, improvisation. We use what we have at hand. Surprised he didn’t look for a small bit of pipe or the wrong end of a shifter for extra leverage on that key.

[Laverda Dave]

Looks like a great idea .. I will have to try it.

On the CB250RS I have just got, it came with a spare caliper but somebody had drilled and tapped the alloy housing to force the piston out and then fitted a short allen screw in order to seal up again (no sealing washer fitted  either) . Ugly looking bodge though IMHO. I have drilled and tapped the piston before, when I knew the piston was knackered (as they usually are). I have never tried the grease gun method but piped up to a master cylinder and used the hydraulic pressure to remove the piston. This is what I did on the seized but unmolested CB250RS caliper that was fitted to the bike.

I think this was only bike that used this caliper Ash.

[K2-K6]

They can be really well stuck from that corrosion around the seal.

The rears on many VAG cars are usually aluminium  caliper and very similar bore to our Honda type, with a seal boot to cover piston. If that seal is compromised though the corrosion builds such that you can't turn them at all, even with proprietary tool engaged.
The mechanical handbrake is concentric with the hydraulic piston too, and can sometime not be operational even pulling the lever hard. The only way to get them out is to pump them with footbrake, then they creek and groan like an old wooden boat in protest as they move. It's literally just the corrosion around the seal holding them, once cleaned and refitted they are fine again.

[andy120t]

I used a method an old American bloke uses on his XS650 on YouTube, same principal but using a large nut and bolt wound out inside the piston, stick an open ended spanner over the bolt then a bar through the ring end to twist while pulling up gradually.  Photos might help with this description 😀

I think I can picture that - I'll try on the rear stuck piston/ caliper...I think that only has one piston!  The great thing is, once something works I start to feel a bit more confident. These brakes had been really getting me down.

[Athame57]

I watched the video, I did wonder if extending the leverage of that allen key with a hollow tube, a handle bar perhaps, would have made it less stubborn though?

[Moorey]

  For less than a tenner on Aliexpress you can buy a complete front master cylinder with lever and a  hose. Just pump it out whilst at your
  bench without all the huffing and puffing. Save that for doing something else.  When done just put it back in the drawer with all your other tools. I
  bet he spends more on gloves.
  And I am a Yorkshireman

[andy120t]

Where's the warm feeling of satisfaction and achievement in that! (Whereas keeping a tenner in your wallet...now there's a fine feeling,).🙂