Sitting close to ground level, your brake calipers are subject to all sorts of contaminants, from dirt, dust, and sand to mud, snow, and salt. As a result, corrosion can form on the caliper bracket and around the caliper piston. The rubber boots that safeguard the slide pins can crack or rupture, impregnating the lubricant inside with dirt and sand and causing the caliper to seize.
Therefore, during a brake caliper service, a mechanic will remove the wheels and tires to access the brakes, inspect the calipers for signs of leaks, remove the caliper from its bracket and set aside the brake pads, and potentially unbolt the caliper brackets. The components are then thoroughly cleaned. The slide pins are lubricated with a special heat-resistant grease, and the components are re-assembled. Any new hardware needed, or replacement of the brake pads and rotors, are additional services that may be requested at the same time.