removing caliper pistons

[mickwinf]

I cant remember who suggested this method but just tried on two old seized calipers and worked a treat. Basically you screw a grease gun end into the thread where the hydraulic pipe fits, only needs a thread or two so even if the threads are different it will still work. Make sure the bleed nipple is tight then pump away until the piston pops out! Comes out quite gently so not dangerous, i now have two calipers that can be re used.

[Bryanj]

Me, messy to clean but worth it, dont forget to use a pick on the groove especialy corners.

[Tomb]

It is a good method.

But why remove the piston pump that comes with the brake - the master cylinder, to fit a different piston pump - a grease gun? I use the master cylinder to pump out the piston.

[Bryanj]

I did cos i had a job lot of used ones and the bikes i had from US had totalled flexibles along with no fluid.

It human nature (at least male anyway) toblast in with the tool before reading instructions oŕ thinking about what might happen later

[McCabe-Thiele (Ted)]

In the past I've used an old Mini Master Cylinder with a flexi hose connector as a tool to pop them out - I haven't used my tool for about ten years so it went in the bin during a garage clear out!

Likewise I gave away my old Technicians Bore Gauge & a set of three micrometres as they were all imperial as was the dial gauge they went to a good home that's my only consolation.

All this decluttering was done in the sure fire knowledge that my days of tinkering / mechanic were long gone.............sigh how wrong I was!

[mickwinf]

Thanks Bryan great idea. I have not got a working master cylinder to use except the one on the bike and did not want to disconnect just for this job.

[Johnny4428]

Don’t think I’ll be the only one to have removed one with compressed air? Not really that clever but did the job. Did it wrapped in rags otherwise you will have a missile. Better and safer to use fluid or grease.

[philward]

The hole in my garage window is testiment to the compressed air method! However, I have had pistons that would not shift with compressed air that I had to use a grease gun on, which shifted the piston.

[Johnny4428]

The hole in my garage window is testiment to the compressed air method! However, I have had pistons that would not shift with compressed air that I had to use a grease gun on, which shifted the piston.

Oops 🤣

[Bryanj]

Yup air only works if they aint siezes, grease just works

[AshimotoK0]

The last three 400/4 ones did last year (which a came from a plastic boxes left in a garden for over 20 years + and were really grotty )  I removed by boring a hole just a bit bigger than the piston in a piece of hardwood then whacking the caliper on the wood so that the inertia of the piston shifts it out gradually. Once the piston is flush with the caliper I then do the same thing over the hole in the wood so that piston can move out fully.
 
I have also removed stuck caliper pistons, by drilling and tapping the bottom of the piston M10 and screwing in an M10 bolt tipped with a bit of nylon (to prevent damage to the alloy) to extract the piston. This is only any use if the piston is knackered but TBH every siezed one I have done has suffered pitting of the crappy chrome.

Personally I have never tried the grease method but it obviously works. I guess it's difficult  if the the rigid  pipe  union is seized/sheared off in caliper body though.

Anyone have tips and tricks  on cleaning out the seal groove? Best tool to use?

[Bryanj]

Dental pick or set of mechanics picks using right angle one to get into corners, then after all the crud is loose possibly a brass brush in a dremel.
I found just using the brush just polished the hard crud and didnt remove it.

[SumpMagnet]

To shift the rear piston on my 750, I had to use a load of heat as well as brute force. Nothing was shifting it.

I assumed the piston would need replacement so I clamped some mole grips on, applied heat until the piston actually shifted a fraction....then I could apply hydraulic pressure to pump it out. There was corrosion on the piston...and a small amopunt in the caliper body...but considering the fight I had to shift it...far less than I was expecting!