Obviously the pistons should move freely but how easy should you be able to rotate the pistons in the caliper - by hand (finger pressure only) or with a pair of piston pliers? How often do you pop the pistons out to smear the seals with red rubber grease? All advice welcome. Thanks
There's no reason that I'm aware of for wanting to rotate the pistons either by hand or otherwise. They should move back and forwards in their cylinders fairly easily. With regard to greasing seals, no idea but not something I would do regularly. Maybe a light smear around the protruding portion of the piston if doing some serious cleaning or after a brake rebuild (if it has a rubber boot but otherwise I wouldn't). I'm always fairly cautious regarding lubricants and brakes.
I recently rebuilt my calipers with new seals. Once re-assembled with new seals and smearing of red rubber grease, I could just about rotate the pistons, but only just. And that was with the calipers halves split, so I was able to get a good grip. On intact calipers that have been used, I don't think you would be able to rotate the pistons by hand.
Brakes should be kept clean enough so that when you come to change pads pistons can be pushed back in by hand. Not sure about smearing with grease after cleaning,never done it,maybe I should tho?
Personally wouldn't and dont put grease on pistons as IMO the dirt will cling onto it, strip and clean with brake fluid only. Pistons should puch in easily with fingers.
Thanks for the replies guys, I am able to push the pistons back by hand but noticed that one was slightly harder than the others and wondered if the seal was getting hard with age hence the thought of apply some grease to keep the rubber more supple. I can rotate the pistons by hand (just) so that also gives me confidence that nothing is sticking.
The one that's slightly harder to push is probably because you're pushing the fluid over to the other calliper then up to the mc.
