RearPiston and Seal

PISTON AND SEAL

Before disassembling the brake caliper, clean and inspect it. Disc Brake Caliper - Inspection.

WARNING: Under no condition should high pressure air ever be used to remove a piston from a caliper bore. Personal injury could result from such a practice.

CAUTION: Do not use excessive force when clamping caliper in vise. Excessive vise pressure will cause bore distortion.

1. Mount the caliper in a vise equipped with protective jaws.




WARNING: Do not place face or hands near caliper and piston if using compressed air pressure to remove piston. Do not use high pressure.

2. Place a wooden block (1) in the caliper as shown.
3. If necessary, apply low pressure compressed air to the caliper fluid inlet in short spurts to force the piston out.
4. Remove the piston from the caliper. Discard the piston.




5. Using an appropriate tool (2), remove the dust boot (3) from the caliper (1) and discard it.




CAUTION: Do not use a screwdriver or other metal tool for seal removal. Using such tools can scratch the bore or leave burrs on the seal groove edges.

6. Using a soft tool such as a plastic trim stick (1), work the piston seal (4) out of its groove (3) in the caliper piston bore. Discard the used seal.
7. Clean the piston bore and drilled passage ways using alcohol or a suitable solvent. Wipe it dry using only a lint-free cloth.
8. Inspect the piston bore for scoring or pitting. Bores that show light scratches or corrosion can usually be cleared of the light scratches or corrosion using crocus cloth. Bores that have deep scratches or scoring may be honed. Do not over-hone the bore. Do not increase the diameter of the bore more than 0.0254 mm (0.001 inch). If the bore does not clean up within this specification, a new disc brake caliper needs to be installed.

NOTE: If honing the bore, during the honing procedure, coat the stones and bore with clean brake fluid. After honing is complete, carefully clean the seal and boot grooves with a stiff non-metallic rotary brush. Use extreme care in cleaning the caliper after honing. Remove all dirt and grit by flushing the caliper bore with fresh clean brake fluid, then wipe it dry with a clean, lint free cloth, and then clean it a second time.