Rear Brake

[Anonymous]

OK.. I got a used caliper from a local shop. My old one has a piston rusted in it. Installed the new used one today. When I compress the pistons, then bleed em, they stay. When I pump the brake the pistons grab but are not retracting to release. I have been working on this all morning and now I am brain fried. ANy ideas as to what I am missing?

[jimcor]

The pads will not visibly pull back. They will continue to lightly ride the rotor.

When you say "retracting to release" do you mean the caliper will not release the rotor? If this is the problem grit and dirt are usually the problem along with piston corrosion. Disassembly, cleaning, light sanding of the piston, replacing worn seals and boots is usually the fix. I would have a manual as a guide when tackling this project.

[Anonymous]

Basically just do a rebuild of the caliper. Clean it real good and what not. kk.. will try that tomorrow. I am tired of messing with it atm.

[jimcor]

Basically just do a rebuild of the caliper. Clean it real good and what not. kk.. will try that tomorrow. I am tired of messing with it atm.

Yeah, things can get frustrating at times. Look on the brite side tho'. You don't have any busted bolts that need engine removal, EDM, retap or helicoil...

[Jethro]

The main thing is to make sure the side pins are clean. These are the pins that the caliper floats on. I would definitely buy new seals for the pins, and make sure you use the right lube on them (I think it's some sort of silicone, but I'm not sure, consult your manual). I think the seals for my 1100 were like $6 per pin, there should be 6 on the entire bike.

As Jimbo said, the brakes are designed to lightly rub on the rotor. That's how they center themselves.

[Anonymous]

Yeah. Most disc brakes touch oh so lightly. These grab and hold as if they are a parking break. Unfortunately I had to order a caliper kit, so I won;t be able to do much til next week. It has been too long since I even touched a motorized vehicle of any sort.

[Anonymous]

Well after several days of tinkering and several trips to the store I got the rear brakes working nicely. The lube I had bough was not the correct type ( had spray and not the sili gel style ). So after looking around and behind some tubes and bottles I found the good stuff. The I got it all lubed up, recut the threads just a hair to get rid of the rust on the bolts and bleeders. Now they are really smooth. I then started on the the fronts. The fronts had to be rethreaded because they were crossthreaded like the clutch perch was. Once that was done the front calipers went together easily and sit nicely. Now I get to rebuild the front MC and the brakes will be alll nice and clean again.

And this is where the attention changes to the wiring...... LOTS of burned out, crudded up, need to just rerun everything type of a job. Not looking forward to this one. But yes, the bike is coming along. Almost there.

[shortlid]

My rear also!!

I was wondering why I was geting 27 MPG on my '80 GS850G so after a burst around town I heard the rear brakes squeaking when I was not on them? So I touched teh front two discs and they were warm but not hot. When I went to touch the rear it was VERY hOT!!
I took the inspection cover off the rear brake caliper. The inboard pad was down to nothing the outboard had meat on it. I took the cover off teh rear tank and it was pretty clean. I sucked it out replaced with new DOT 3 and went to bleed the brakes and RUST COLORED FLUID CAME OUT of the rear caliper bleeders!! I pulled the pads and hardware out and pushed on theout board piston got it to go in. The inboard piston would not budge!! What are my options here guys?? :roll:

[BigMattyD]

In my experience, it takes more than a little hand pressure to press the piston into the caliper. Try using a c-clamp.

The only time I could get the piston in by hand pressure alone is when I rebuilt the caliper. The piston slid all the way in with hand pressure, but once it's in, they don't seem to move in or out with anything but a large amount of force.

The only way I can pop them out of the caliper is to attach the brake hose and pump the brakes till the pistons are almost fully extended. Then you can pull them out.

I think that if there is even a little fluid behind or around the piston, there is too much hydraulic tension (if that is the word) to allow free motion. It is like when you get your foot stuck in the mud, and can't easily pull it back out.


Matt

Note to self: Remember to get a jar of that brake caliper lubricant...

[shortlid]

Should I just bleed and try?

Are you saying I should just bleed it real good and try to get it to work better? NO rebuilding would be good!