Bottom the piston into the caliper bore, noting the following:
There is a special spanner-type tool designed to fit in the piston slots. This allows you to turn the piston and thread it into the caliper, retracting it. Use care if using a substitute tool. Careful work with suitable pliers may enable you to turn the piston back into its bore.
After bottoming the piston, lift the inner edge of the dust boot, next to the piston, and press out any trapped air. The boot must lay flat.
Make sure the slots in the end of the piston are positioned "horizontally" when looking at the caliper with the mounting bolt holes at the 12 o'clock and 6 o'clock position. The slots in the piston must be in this position before pivoting the caliper down over the brake pads in the caliper support.
Install the two pad clips in the brake caliper support. Whenever new brake pads are installed, these clips should be in the new disc pad kit.
Install the outboard and inboard brake pads in the caliper support. The wear sensor is on the outboard pad. The sensor is positioned downward at the leading edge of the rotor during forward wheel rotation. Hold the metal pad edge against the spring end of the clips in the caliper support. Push the pad in toward the hub, bending the spring ends slightly, and engage the pad notches with the support abutments (the machined edge of the caliper support).
Pivot the caliper down over the brake pads. Take care not to damage the piston boot on the inboard side of the caliper. Compress the sleeve boot by hand as the caliper moves into position to prevent boot damage. After the caliper is in position, recheck the installation of the pad clips. If necessary, use a small flat-blade tool to re-seat or center the pad clips on the caliper support.
Install the mounting bolts and tighten to 20 ft. lbs. (27 Nm).
If removed, install the parking brake support bracket (with cable attached). The bolt is tightened to 32 ft. lbs. (44 Nm).
Install the tire and wheel assembly, aligning the balance marks made at removal.
Lower the vehicle.
Fill the master cylinder reservoir to the proper level using only fresh, clean DOT 3 brake fluid. Pump the brake pedal firmly to push the pistons back out into operating position and to seat the lining.
After the brake pads have been replaced and/or rotors have been refinished, GM recommends that new brake pads be broken in, or "burnished". Use the following procedure:
Make 20 stops from 30 mph using medium to firm brake pedal pressure.
Take care to avoid overheating the brakes.