Disc Brake Caliper
| Refer to COMPONENT INDEX . |
Dual piston (2) disc brake calipers (1) are used on the front. Single piston (5) disc brake calipers (4) are used on the rear. The calipers are free to slide laterally, which allows continuous compensation for lining wear. The rear brake calipers provide the mounting and connection points for the EPB actuators (3).
Petroleum based grease should not be used on any of the rubber components of the caliper. Use only Non-Petroleum based grease.
Identifying Front Caliper Components
When the brakes are applied, fluid pressure is exerted against the caliper piston (2). The fluid pressure is exerted equally and in all directions. This means pressure exerted against the caliper piston and within the caliper bore will be equal.
Fluid pressure applied to the piston is transmitted directly to the inboard brake pad (5). This forces the inboard pad lining against the inboard surface of the disc brake rotor. At the same time, fluid pressure within the piston bore forces the caliper to slide inward on the mounting bolts. This action brings the outboard brake pad lining (6) into contact with the outboard surface of the disc brake rotor.
In summary, fluid pressure acting simultaneously on both piston and caliper, produces a strong clamping action. When sufficient force is applied, friction will attempt to stop the rotors from turning and bring the vehicle to a stop.
Application and release of the brake pedal generates only a very slight movement of the caliper and piston. Upon release of the pedal, the caliper and piston return to a rest position. The brake pads do not retract an appreciable distance from the rotor. In fact, clearance is usually at, or close to zero. The reasons for this are to keep road debris from getting between the rotor and lining and in wiping the rotor surface clear each revolution.
The caliper piston seal (4) controls the amount of piston (2) extension needed to compensate for normal lining wear.
Caliper Operation
During brake application, the seal is deflected outward (6) by fluid pressure and piston movement. When the brakes (and fluid pressure) are released, the seal relaxes (3) and retracts the piston (1).
The amount of piston retraction is determined by the amount of seal deflection. Generally the amount is just enough to maintain contact between the piston and inboard brake pad.