Conceptual

Brake Caliper Piston Retraction

New, thicker pads need the caliper piston pushed fully back into its bore — with a C-clamp or spreader against the old pad, slowly, with the reservoir cap loosened and fluid level watched so it doesn't overflow. On a Prius this is only safe after the actuator is disabled; never force a piston at an angle or you'll cock it and tear the seal.