Stromthusiast!
Join Date: Dec 2010
Location: Arlington Texas
Posts: 37
Brake caliper piston operation
Caliper pistons are supported in their bores by flexible seals ( one or two), which sit in grooves cast ( or machined in) the bore. The seal has a slight grip on the piston ( tight fit ) and when pressure is applied to the caliper the the piston moves deforming the seal slightly. This movement forces brake pad into contact with brake rotor. When pressure is released the seal returns to it's original shape and pulls the piston back slightly.
This is why cleaning calipers of brake residue at each tire change and changing brake fluid every couple of years is such a key part of brake maintanance. Failure to do so may eventually cause the piston to stick in it's bore and not retract causing overhreating and /or premature pad and rotor wear.
As for caliper cleaning I remove the pads, noting original install and using a catch pan or bucket for containing the mess which follows do a vigerous scrubbing with a toothbrush and dilute Simple Green or suitable detergent then followup with water rinse and dry. Spray brake cleaners sometimes contain chlorinated solvents which can be pretty tough on piston seals in my opinion so I avoid these.