Brake Caliper Press
A specialized tool used to compress the piston or pistons of a brake caliper back into their bores when replacing brake pads.
A brake caliper press (also called a caliper piston spreader) is a specialized mechanical tool used by technicians during brake pad replacements. As brake pads wear down, the caliper pistons extend further out of their bores to keep the pads in contact with the rotor. Before new, thicker brake pads can be installed, the caliper pistons must be pushed completely back into the caliper housing, creating the necessary clearance for the new pads and rotor.
The caliper press features dual or quad plates that expand outward when a central ratchet or screw mechanism is turned. This design applies even, parallel pressure across the face of the caliper pistons, pushing them back smoothly without tilting or binding them in their bores. Using a press is especially critical on multi-piston calipers (common in high-performance and heavy-duty vehicles), where compressing one piston can cause the adjacent pistons to pop out if not held in place.
Before using a caliper press, it is standard practice to clean the exposed piston walls of brake dust and debris to prevent damaging the rubber piston seals as they retract. Additionally, the master cylinder reservoir cap should be removed or a bleeder screw opened, as retracting the pistons forces brake fluid back up into the reservoir, which can cause an overflow.