I know that this is an older post, but knowledge doesn't really doesn't really date that much. Before I pull the caliper on this sort caper, I leave one pad in one side and take the opposite one out and use it to cover one piston. I then work the brake to see if the single piston is coming out to play. I then remove the loose pad and try the next piston and so on until all 4 have had a shove. This lets me know what I am in for and doesn't damage anything. If I get one that won't play, I'll keep trying pedal pressure to move it. Possibly use a clamp to push the piston back into the cylinder to create movement. I keep doing this until the piston is freed off enough to move in and out. OK if it's solid - totally, I then disconnect the brake line and try the compressor in there. A blast of air at 150psi sometimes shifts the offending piston. Any work that you can do whilst it's on the vehicle is a bonus in my view. OK, if it has to come off then I try to leave the other pistons in with small clamps stopping them from flying out. This keeps the crap out of the cylinders and of course means that if you run out of time, it can go back on the vehicle for now. My experience is that if you try to rotate the pistons in the bore, the seal actually 'wrinkles up' in a way and simply jams the movement. As they are worn, there is crud in there and the seals are usually adhered to the piston, rotating them only causes damage to the lip of the piston where you grip it. OK this doesn't affect the braking when you put it all back together, but it offends my sense of professional pride!. The best way for them to come out is straight. You could tack a small bar across the mouth of the piston and use that to pull on to get the piston moving, I guess. Anything but water pump pliers!
If you do rotate, then just wiggle back and forth a very small amount. As I said, trying to spin the piston is not the best method. As soon as you get any movement, capitalise on it. Just keep it going back and forth or in and out to consolidate the free space. Get some brake fluid in there or grease to lubricate it until the movement increases. Major damage to the chrome plating will let the elements in over time and cause you grief again. I treat mine with some Kurust or something to kill any corrosion and form a barrier.
I have done this once or twice and vowed some while ago never to abuse pistons again. Brains over brawn I think. (Then I start whacking the sodding thing)
Chris
I obtained my refurb kits from Ian too!
