04-05-15, 10:00 PM
Often times they look much worse than they actually are. 
The spring at the bottom of the caliper comes out with a bit of fiddling, it is to keep pressure on the pads and stops them rattling. Replace the slid pins also.
The alloy wheel cleaner will get most crap off the piston also without damage, I normally use a sharpen piece of very hard plastic as a scraper for the tough bit and since it will be softer than steel it won't damage the pistons. Not to keen on using wet and dry.
The spring at the bottom of the caliper comes out with a bit of fiddling, it is to keep pressure on the pads and stops them rattling. Replace the slid pins also.
The alloy wheel cleaner will get most crap off the piston also without damage, I normally use a sharpen piece of very hard plastic as a scraper for the tough bit and since it will be softer than steel it won't damage the pistons. Not to keen on using wet and dry.