This isn't actually the usual question. I've had a very slightly sticky rear piston (on an A6 1996 model ) so I've overhauled the calipers to see if that does the trick. I've got one of the two back together and I've screwed the piston back in till it's almost flush with the boot - it's about 1mm proud of the boot. Is that far enough? What a sod of a job, incidentally. I don't want to force it further because I'm worried about damaging the boot as I'm having to grip the end of the piston to turn it.
Then I thought, since I'm not replacing the pads, which have plenty of life left, should I have retracted the piston all the way? I think probably the answer is yes, and that the handbrake mechanism will sort itself out, but can anyone confirm.
Second, presumably the procedure when I 've got the caliper back on the car is to take up the slack by pumping the pedal till the piston hits the pads tight against the disc, and then leave the self-adjusting handbrake to do itself.
Incidentally the seal kit had some pinkish gunk which you soak the piston seal in for at least 45 minutes. I've never seen it before. What's going on with that? It doesn't make re-fitting the piston any easier without the special tool. I only soaked the seal itself and not the boot. Should I have soaked both?
Amazingly the caliper, pistons and handbrake mechanism all seem in good condition, so that's one thing Audi have improved since the 1980s.
Thanks for any advice.