As the brake pedal is released, how do caliper pistons pull away from the rotor?

The caliper pistons pull away from the rotor primarily due to piston seal deflection. When the brake pedal is released, the hydraulic pressure in the brake line decreases, allowing the caliper pistons to move back slightly. This movement is facilitated by the elasticity of the seals around the pistons. These seals are designed to slightly retract when pressure is lost, creating a pulling action that draws the pistons away from the rotor.

This mechanism is crucial for ensuring that the brake pads disengage from the rotor effectively, allowing the rotor to spin freely once braking has ceased. The function of the seals helps prevent drag on the rotors, which can lead to overheating and premature wear of both the pads and the rotors.

While other options involve components related to the braking system, they do not specifically address the mechanism by which the pistons retract from the rotor after the brake pedal is released. The master cylinder springs likely pertain to the overall hydraulic system but do not directly influence the piston movement in this context. Similarly, a return spring typically would be associated with other braking components, and hydraulic vacuum is not involved in the retraction of caliper pistons.