stuck caliper piston

Tim_S · Sep 26, 2011

I've had pretty good luck over the past few years removing stuck caliper pistons but this one gave me a fight. I had to resort to a more aggressive approach and use excesive force. The out board caliper came loose with just compressed air but the inboard one won't budge. Some head scratching ensued and i got out my grease gun and some more tools. After about an hour or so of the greasey mess I could see some progess but my sticky mess was hindering me. I had to figure out a way to confine my loose piston so the force would transfer over to the rear. Once that was accomplished with a C-clamp and some flat stock steel I pumped more grease in and out it came. Where there is a will there is a way. Some of you may have tried this method or some may have only thought what if ..........? GO FOR IT !

Tim_S

Hobot · Sep 26, 2011

How does one fit a grease gun nozzle into the caliper? replace bleeder with off the shelf zerk?

powerdoc · Sep 26, 2011

I bought a Zerk at NAPA

aceaceca · Sep 26, 2011

Another method is to drill a hole in the center of the housing so you can insert a drift to help the piston out. When done ,tap the hole for a blind allen headed plug. Some heat also does wonders .

Hobot · Sep 26, 2011

Ok cool a zerk and clamping the outer puck is are the keys to the greaser method.
For a entirely stock unmolested example one don't want to put even a tiny beauty spot required in the almost hidden back flat of the caliper, so resorts to the smacking or drilling the ruined puck to suck out. After seeing the hassle involved with I made a preventive maintenance hole in my special project to just make it a routine procedure to service. More than one way to skin this cat.

Tim_S · Sep 26, 2011

Yep, I used a regular zerk that can be found at the local harware store. I also use a modified bleeder screw for the times I use compressed air. Filed the tapered end flat to open up the hole and whittled down the top side to a point that would fit in the end of my blow gun. One thing to remember just because the piston is stuck doesn't mean it isn't any good. The bore on the caliper was in good shape to, no pitting.
This one happened to be good and the out board piston was rusted real bad from exposure. I'll reuse it. I personally wouldn't drill a hole in the back of a caliper. But that's just me,,,,,,,, :roll:

Tim_S

swooshdave · Sep 27, 2011

aceaceca said:
Another method is to drill a hole in the center of the housing so you can insert a drift to help the piston out. When done ,tap the hole for a blind allen headed plug. Some heat also does wonders .

Primitive. :cry:

Hobot · Sep 28, 2011

Primitive is as primitive does but I shudder at wisdom of economy to put the rust prone factory pucks back in as the next guy may not have your mettle of fettering.

http://www.oldbritts.com/ob_start.html

If they'd leave a bit of a boss in the middle with treads tapped, one in face one in the back then could just screw in a puller outer for straight forward servicing.

swooshdave · Sep 28, 2011

hobot said:
Primitive is as primitive does but I shudder at wisdom of economy to put the rust prone factory pucks back in as the next guy may not have your mettle of fettering.

If they'd leave a bit of a boss in the middle with treads tapped, one in face one in the back then could just screw in a puller outer for straight forward servicing.

http://www.oldbritts.com/14_061896.html

debby · Sep 28, 2011

swooshdave said:
aceaceca said:

Another method is to drill a hole in the center of the housing so you can insert a drift to help the piston out. When done ,tap the hole for a blind allen headed plug. Some heat also does wonders .

Click to expand...

Primitive. :cry:

It works though!

But using a cheap wobbly Harbor Fright drill press to drill the hole is not recommended...

Debby

B+Bogus · Sep 28, 2011

This brings back memories!

I had the same issue, and I managed to get a pair of tyre (note correct spelling

) levers into the inboard piston, and with a bolt wedged in as a pivot I squeezed the other end of the levers in the vice to grip into the bore of the piston. With the application of a little heat it wormed its way out nicely.

The pistons went straight in the bin and stainless replacements were used.

With a modded front Master cylinder the brake was OK, but with my daughter on the back it lacked feel, although it would squeal the tyre (Note again

) if squeezed hard enough.

Although a major investment, I CAN highly recommend this setup (from RGM in the UK) if you like to hustle the bike at all...
Two-finger braking, and totally confidence inspiring.

Stillreel · Oct 1, 2011

I'm dealing with exactly the same issue and I have a question regarding the outer cylinder hydraulic port. In my effort to free the outer piston, I have pressed further in by 1/16 - 1/8". I want to try the grease method but I'm worried that I may have covered the hydraulic port with the piston. Is the hole on the bottom or the side of the cylinder?

Thanks
BC

powerdoc · Oct 1, 2011

Are you referring to the side where there is no access hole? If so, the hydraulic port is almost at the end of the bore. If you're talking about the side with the access port, it's about 1/4 inch from the port threads.

Stillreel · Oct 1, 2011

The stuck piston is the one where there's no access. Currently, the top of the piston is 1/4" below the inside flat surface of the caliper. I can see a 1/16" of it in the slot where the brake shoe pad tab fits. I really hope this thing is going to pop out. I'll try heat as well but I thought the dishwasher idea was pretty innovative too.

BC

Stillreel · Oct 1, 2011

If I knew the depth of the cylinder, I could figure out how far from the bottom it was as well, and then maybe if it is covering the port.

powerdoc · Oct 1, 2011

Dude, you'd have to push it through the aluminium to get it past this hole! Try it, worst thing that'll happen is it won't move.

Stillreel · Oct 1, 2011

Got it!

Here's the new standard for removing lower stuck caliper pistons:

put into dishwasher on hot cycle (also gives the part a sparkling clear finish!)
once out and while still hot, blast piston with an inverted compressed air can, (dry ice temperatures) to break seized surfaces
apply oil to rim of piston
apply compressed air to hydraulic port, ensuring bleed port is closed/sealed.

Note: probably best to wait until the wife is out.

The caliper body looks good but both pistons badly corroded. Stainless steel or aluminum replacements??

BC.

pete.v · Oct 1, 2011

Good work.

Stainless steel.

stuck caliper piston

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