Front Discs

Each front disc brake assembly consists of the following components.

• Caliper - single piston, floating type.
• Caliper adapter.
• Shoe and lining assemblies.
• Rotor.

The caliper is a one-piece casting with the inboard side containing a single piston cylinder bore. The front disc brake caliper piston is manufactured from a phenolic compound. The outside diameter of the caliper piston is 57 mm. A square-cut rubber piston seal is located in a machined groove in the caliper cylinder bore. This seal provides a hydraulic seal between the piston and the cylinder wall. See Fig 1 . A rubber dust boot is installed in a groove in cylinder bore opening and in a groove in the piston. The boot prevents contamination in the bore area. The caliper is mounted to the caliper adapter using 2 guide pins, slid into the adapter. The pins are lubricated and have boots to seal them in place in the adapter. The disc brake caliper adapter is fastened to the steering knuckle using 2 bolts. The machined abutments on the adapter position the brake shoes and caliper. There are 2 brake shoes, sometimes referred to as pads, per disc brake. One shoe is placed on each side of the brake rotor. Two abutment shims (upper and lower) ride between the shoes and adapter. The shoes have springs permanently attached to them to help maintain a distance between the shoes and the caliper. Front disc brake are equipped with audible wear indicators on the inboard brake shoes. Each front brake rotor is vented to help cool it during and after brake applications. It is mounted on the studs of the front wheel bearing hub. This vehicle has an optional performance brake system. The sales code for this system is BR4. Although similar in appearance to the other disc brake systems available (BRB - disc/drum and BRT - disc/disc), this system features heavy duty wheel brake components. BR4 front disc brakes utilize brake rotors that have a pad contact surface approximately 5 mm thicker and brake calipers (and adapters) to accommodate that additional width. See Fig 2 . The BR4 calipers and rotors can be easily identified. Each BR4 brake caliper is marked TURBO while each rotor has a recessed machined area near the hub center. See Fig 3 .