Rear Brakes sticking Options

[crankyelbow]

At first I thought it was the parking brake - as it was in dire need of being adjusted. I adjusted and the parking brake worked wonderfully... but it exposed the problem to actually be the rear calipers sticking closed enough to cause problems.

A few weeks ago I noticed the drivers rear wheel was hot/smelled like I had just had run a few hard laps... but it seemed to cure itself. Then the passenger rear started sticking - bad! To the extent I thought my clutch was burning out as I had coincidentally been experimenting with getting started in 2nd gear. But as I paid more attention to the problem, I noticed the car would not roll freely as it was supposed to - when I expected it to roll back/forward on slight inclines it stayed put even though I could feel it should be rolling.

I jacked the car and noted that I could turn the passenger rear wheel, but it took a bit of effort AKA not free spinning at all.

So yesterday I pushed in the piston on the right rear which seemed to cure the problem, only to notice after getting off the highway that the left rear was still sticking slightly, enough to get stinky but not enough to lock the car in place.

Today I'll push that piston in, but what could have initially caused this issue? How can I hope to resolve it permanately? Luckily the calipers are cake to get off, but I don't want to have to keep doing this over and over?