I/S Rear Brakes Dragging

[BINOVC]

Recently both of my I/S's started having issues when I leave for work and apply the rear brake, they "have trouble" releasing.  Meaning it won't free-roll, need to apply power.  At some point, I decided to just keep riding, and found that eventually they would work normally again.  Maybe within a mile or so of neighborhood roads.
Last Summer I replaced the rear pads and the fluid in one, and removed and cleaned up both caliper pistons.  Seemed to be working just fine.
I usually get in at least one good commute per week per bike (I have 3 that I need to keep exercised).
Wondering if this might be a symptom of needing to replace the seals.
If so, are there seal choices available and possibly recommendations as to which to get?

[old2soon]

when I have/had that issue the pistons WERE in fact crudded up. and if ya pull the pistons to clean may as well rebuild the caliper while yer at it. two rubbers or O-rings per bore. RIDE SAFE.

[sandy]

Valk new to me last Dec. I rebuilt my front calipers due to dragging. Still dragged. Took back apart and found corrosion under the new seals. Had to scrape it out so the new seal would seat all the way into the groove. The Valk had spent it's life on the east coast with lots of humid salt air. The hydraulic fluids looked like they had never been flushed.

[Jess from VA]

When I really do a thorough clean job on my bikes, I start on the wheels/brakes and underside with a little water and then spray liberally with S100 (or other mild corrosive wheel cleaner).  Then scrub hard with stiff bristle brushes (nitrile gloves and eye protection). One wheel at a time. Then hose off, then back over it all with warm soapy water (to get all corrosives off), then the rest of the bike.  Then blow it off thoroughly with a Stihl leaf blower, then wipe it down.

This always has a very positive effect on my brakes smooth function, including a better feel from the handlebars.

When doing more detailed brake cleaning at tire changes, I use gun cleaning solvent and old beat up bronze and brass bore brushes on a pistol rod (pushing the pistons out, but not all the way out).  And grease the pad slider pins, but not the pads.











  

[da prez]

  I remove and clean and lube the caliper slides also. The caliper will release the pads , but if the slide pins and hardware are dirty , they will stick. Do the entire job and problem should be solved.
  When rebuilding the caliper , the seal seats must be cleaned or the pistons will stick. The square O-ring shape is what releases the caliper piston.

                                       da prez

[BINOVC]

Definitely haven't been washed in a while.
So I'll just clean up the pistons again, make sure I get the seal seats good, and re-lube the caliper pins.
Thanks!

[Highbinder]

Another thing you might want to check is the pivot pin where the rear brake arm is..this is suppose to be a maintence area to be checked, in side the pivot area if I remember correctly is an o-ring and should be greased.  If this dries out the brake doesn't release all the way, creating a drag on the pad, when removing the brake pedal look behind for a lock nut before you try to remove it, if you don't you,ll break the pin bolt, this I know for a fact.. ;Dl  I had this happen to me on my I/S cleaned it up, re-greased and solved the dragging brake problem.  Look in your shop manuel for instructions.

[revks]

I started to go for a ride on my newly acquired 2000 I/S two days ago and the front wheel locked up. Turned out to be the brake calipers.
It took a lot of coaxing to get the pistons back enough to get the right one off, but I finally did.
It took even more coaxing to get the pistons out. I usually apply air to the brake line port and they come right out. These didn't! Actually removed the pads and bolted the brake line back on and used the master cylinder to push the pistons all the way out.
A lot of corrosion built up in the grooves for the seals pushing them against the pistons.
after a thorough cleaning of pistons and grooves and replacing the seals the pistons slid in easily.

I experienced the same thing with the 1983 Yamaha Venture I used to ride. Seems these alloy calipers are prone to corrosion build up especially behind the seals. You can't see it or fix it without removing the seals.