Front brakes.

[vinnyb]

I wouldn't use anything abrasive on caliper pistons or take them out without replacing the seals, the lips are easily damaged. It might be worth pumping out the pistons with a block of wood between them so they don't pop out them giving them a good clean with a toothbrush and brake cleaner then use red rubber grease on them and work them in and out a few times. Remember to wipe the excess grease off it'll attract all sorts of crap it you don't. Hope this helps, good luck.