Rear Caliper Stripping and Cleaning?

[Meuryn]

Hey everyone,

My rear brake has been rubbing after the fitment of new pads, the wheel alignment is spot on so it isn't that, and from the looks of things, the pistons apply pressure but don't 'retract' enough to stop the pads rubbing against the disc. I had real trouble getting one of the pistons back into position fitting the new pad, it eventually gave way and slid back nicely, but I'm a little worried I might have damaged something in the process? The disc is consistently getting too hot to touch after riding. I think the pistons need new seals and a good clean.

Is there a thread / guide already out there on the process? If not, can anyone give me any advice before I forge on? Taking apart the caliper isn't something I've done before, although I'm fairly happy with the bleeding / replacing brake fluid side of things. Bike is a UK '02 model with stock Tokico caliper.

Thanks in advance!
Meuryn.

[dinkydonuts]

Hey everyone,

My rear brake has been rubbing after the fitment of new pads, the wheel alignment is spot on so it isn't that, and from the looks of things, the pistons apply pressure but don't 'retract' enough to stop the pads rubbing against the disc. I had real trouble getting one of the pistons back into position fitting the new pad, it eventually gave way and slid back nicely, but I'm a little worried I might have damaged something in the process? The disc is consistently getting too hot to touch after riding. I think the pistons need new seals and a good clean.

Is there a thread / guide already out there on the process? If not, can anyone give me any advice before I forge on? Taking apart the caliper isn't something I've done before, although I'm fairly happy with the bleeding / replacing brake fluid side of things. Bike is a UK '02 model with stock Tokico caliper.

Thanks in advance!
Meuryn.

Are you sure you aren't unintentionally leaving your foot on the brake while riding? Are the new pads possibly too thick? Disc brakes generally will operate with some small amount of friction between the rotor and pad when the brake isn't applied. This is so that water on the rotor is wiped off continually so you can brake when it's raining.

If the problem really is the caliper, you can see if a shop can rebuild it for you, but you could probably just buy a new one on eBay for less than $40.

Also make sure you are using something like CRC Synthetic Brake Grease on the pins so the pads can move freely.  It also helps to put this on the back of the pads (and in between the pad and the metal shim) to prevent noise.

[gsJack]

Riding year around here in NE Ohio the salt capital of the universe I've had that problem on bikes in general including the GSs.  Had brakes tighten up so tight I could hardly get home to fix them. For a long time now including my 180k GS miles I've popped the caliper pistons and thoroughly cleaned them with steel wool or green kitchen pads or equivalent and then reassemble and bleed them every time I replace pads.  Works for me, depends on your environment if you need to do the same.

Time comes when you can't even get the badly rusted calipers apart anymore and the are also badly worn.  I replaced both calipers and rotors with like new ones from ebay breakers last year at 100k miles on my 02 GS at a tenth of oem new part prices, should have done it sooner.

[Crasm]

Had the same issue but on the front brake , i put new pads in which made it even worse
I released the presure of the system at the bleed nipple and checked opperation of the
Leaver , which felt crap and would not return fully without help.

So i rebuilt the front mastercylinder with a rebuild kit and while it was off i removed the caliper   and cleaned and degreased and then packed it all out with copper greased refitted
Pads and fully reassembled and touch wood its been fine since.

Im not saying its definatly your problem but sounds similar to mine , i did check the caliper seals before i did anythin and they seemed fine so i concluded a good clean and regrease would
Would be fine

[Meuryn]

Ahh, ok. Yep, I ride throughout the winter here in the UK and the bike routinely gets covered in salt, so it might well be dirt and corrosion, although nothing looks so far gone in there that I feel straight off it the caliper needs replacing. The pads rub when it's on the center stand and I'm off the brakes (to the point where the wheel stops almost immediately when I try to spin it), so I don't think its just the normal amount of 'water displacement' rub. Either way, would a normal amount of rub cause the disc to get so hot I can't touch it?

If I can avoid changing the seals I will, don't want to wait around while ol' snail mail delivers them I'll start by greasing the pins (they're pretty dirty), then if the brakes are still rubbing I'll pull it all apart and clean and grease everything. I've got some DOT 4 on the ready so I'll replace the fluid and bleed the system while I'm at it. Is it safe to use copper grease? Just a bit concerned it could get washed off and onto the pads and disc?

Thanks for the help, I'll report back when I'm done 
Meuryn