Rear Caliper ?

[Johnny Glenn]

Thanks for looking in - I noticed my rear pads looked thin so thought I'd put some new ones on.....and now of course I've got a real problem! While trying to press pistons back - one wouldn't budge. Read on the forum to push brake and now the one piston that did retract won't push back out?! :bang head:How do I get the piston to come out?! The first one that wouldn't press in - in the first place has been pushed completely out and I notice it's pretty dirty inside so I'm thinking of replacing seals etc but is there a way to get the other one out? Thanks

 

[Redbone]

While it sounds like your in for a rebuild of the calipers, to get that puck back into the caliper you will have remove the caliper and use a large "c" clamp to get it to move.

 

[satariel666]

Thanks for looking in - I noticed my rear pads looked thin so thought I'd put some new ones on.....and now of course I've got a real problem! While trying to press pistons back - one wouldn't budge. Read on the forum to push brake and now the one piston that did retract won't push back out?! :bang head:How do I get the piston to come out?! The first one that wouldn't press in - in the first place has been pushed completely out and I notice it's pretty dirty inside so I'm thinking of replacing seals etc but is there a way to get the other one out? Thanks

You may have air in the fluid - you may try to bleed it.
Also the fluid may be old.

I suggest disassembling the caliper and inspect the seals.


You may try to blow some air into bleeder to make the piston out btw.

 

[Johnny Glenn]

Thanks - Where I'm at is one piston or (puck) totally out after I pushed brake pedal and the other didn't move and is stuck nearly all the way in - maybe a 1/4 inch out. I've taken caliper off - tried to pull on it w/ vice grips - not too much pressure etc until I checked w/ the forum?! I've taken caliper apart, loosened bleeder screw - just don't see other than brute force how to make it come out? Air pressure?

 

[[email protected]]

Remove brake line from caliper
Remove bleed nipple from caliper
Remove caliper from bike
Put air pressure through bleed nipple hole to push out piston. Place a thin piece of wood in there as the piston can come out with a vengence. Keep fingers away!

Clean up the pistons with scotchbrite or fine sandapaper. Clean inside of the caliper. Inpect the seals. Most likely they are reusable unless they are torn, dry rotted, or already leaking.

Coat pistons, and seals lightly with clean brake fluid. Start pistons into bore by hand. May need a c-clamp to press in completely but shouldn't take a whole lot of force. Press in as far as possible

Drain the brake line and reservoir. Remove any glazing from brake rotor. Install pads in cliper. Mount caliper, attach brake line. Use new banjo bolt washers. Fill with new dot 3 or 4 and bleed.

* EDIT* I've had one piston stick on me before and it was a bit tough to get out. I installed the piston that was moving easily but clamped it in place and then blew air through the bleed nipple hole to remove the stuck one.

 

[Fire-medic]

The best way to deal w/this is a complete disassembly and cleaning, and using an overhaul kit. You probably have enough of a buildup of corrosion that things are not going to move easily, if at all.

If you decide to follow Mike's instructions but you can't get one piston to move with using compressed air to force the stuck puck out, I have the solution. Notice your bleeder valve (some calipers have 2)? What is it shaped like besides a bleeder valve? Ever greased a suspension fitting? There is your answer. Use a grease gun to pump the caliper full of grease. I guarantee it will come unstuck where it won't if you try the compressed air method and nothing budges!

I did this helping a friend re-do his CBR600 F2 front brakes. We went to a garage to use their compressor as he didn't have one, and when that didn't work, I suggested the grrease gun, and it immediately moved the piston where repeated attempts w/air pressure failed to budge it. Try it- it works every time!

If you already removed 1 piston, you will have to reinstall it and replace the pads so you hold that one already loose in-place while you allow the other one to move. A c-clamp can hold one piston stationary while you force the other one w/the grease.

 

[alorio1]

+1 on the grease gun, but you need to clean up Orings ASAP after you get piston out. Some Orings will swell if petroleum products come into contact with them.

 

[Saml01]

Read on the forum to push brake and now the one piston that did retract won't push back out?!

Sorry to hijack, but what do you mean "push brake"?

 

[Johnny Glenn]

Thanks for all the advice -- the air didn't work -- great idea on the grease gun, I'll try it tomorrow.

Sam - "push brake" -- I read if piston sticks or won't close to try pressing brake pedal to push them back out, clean and try again. I tried that and the one which was not closing moved but the one which had closed ok didn't come back out?! I was of course trying to close the pistons to make room for the new pads when things got hectic. I've never did any brake work on the bike in 13 years so thinking things were going to go smoothly was wishful thinking!!

Appreciate all the help!

 

[vmaxcruzer]

Ha! Keep fingers away. Yeah, no kidding, theres a story there I MAY tell sometime.

 

[Saml01]

Thanks for all the advice -- the air didn't work -- great idea on the grease gun, I'll try it tomorrow.

Sam - "push brake" -- I read if piston sticks or won't close to try pressing brake pedal to push them back out, clean and try again. I tried that and the one which was not closing moved but the one which had closed ok didn't come back out?! I was of course trying to close the pistons to make room for the new pads when things got hectic. I've never did any brake work on the bike in 13 years so thinking things were going to go smoothly was wishful thinking!!

Appreciate all the help!

Oh I understand.

I know what you are talking about with the caliper. When I looked at the caliper on my bike during a break job it was mangled. The previous owner was a fucking moron. He chewed up the piston and the rotor using it as leverage to compress the piston with god knows what tool.

When using a c clamp make sure to push from the middle using a metal disc or old brake bad resting on the piston. If you try to push on an edge it will not compress. I personally use a spark plug gap gauge, its the perfect diameter.

 

[one2dmax]

Those seals are so basic I hardly ever need to replace them. The calipers usually just need to be taken apart, remove the seals, clean the bores, polish the pistons, and put it back together again.

Sean

 

[Fire-medic]

+1 on the grease gun, but you need to clean up Orings ASAP after you get piston out. Some Orings will swell if petroleum products come into contact with them.

I assume that the average person who is venturous-enough to disassemble his brakes is going to clean them thoroughly after disassembling them completely, but I suppose there is the occasional moron, so yes, "be sure to remove all traces of grease immediately upon disassembling the caliper when using the aforementioned method!"

That reminds me of the RV owner who put the thing on "cruise-control" to go in the back to mix a drink, and sued the manufacturer when the rig went off the road! :rofl_200:

 

[one2dmax]

I use compressed air to get them apart. Isn't always easy but it works.

Sean

 

[Johnny Glenn]

It doesnt want to budge!! Tried grease gun w/ no luck (standard size gun w/ me putting alot of pressure) - I closed off port that grease did come out of but the piston will not move. I'm going to try air and grease gun some more but wanted to see if anyone thinks some heat would be ok? Thinking of heating up the puck and surrounding cylinder lip to see if that could persuade things?!

 

[one2dmax]

If the grease can't hydraulic it out then it's probably a lost cause.

 

[Fire-medic]

Did you thread a bolt into the brake line fitting? If you did and your hand grease gun won't move it you could always take it to a local garage & try their grease gun. If a grease gun won't budge it I am afraid Sean is correct. when you do the grease gun method you want the grease to do the work. Wrap the bolt into the hose female fitting on the caliper w/Teflon tape & don't force it to the bottom of the threads where you would damage the taper for the hydraulic hose. Get a bigger grease gun which develops more psi pressure.

 

[Johnny Glenn]

Thanks -- finally got it! I tapped the piston on my vice a few times and that seemed to get its attention. The grease gun did the trick ater that. I'm now having a problem w/ bleeding - it doesn't seem to like the way I'm doing it? I'll post a new thread to find the answer on correct process - thanks again everyone!