6. Caliper: removal, examination and refitting

  1. The caliper assemblies are identical in design and construction whether fitted to the front or to the rear brake. In both cases, it will be necessary to remove the caliper from the fork lower leg or from the final drive housing as appropriate. Each caliper is retained by two bolts.
  2. The caliper units should be removed for overhaul if there has been any evidence of weeping from the seals. Note that seals can sometimes leak enough to admit air to the system without allowing the fluid to leak out. Whatever the case, immediate investigation is warranted. Start by disconnecting the brake pipe at the caliper gland nut and block the open pipe end with a suitable wooden or rubber plug. This will prevent the ingress of contaminants and the loss of hydraulic fluid.
  3. Take great care during the dismantling and reassembly sequences, that no hydraulic fluid is allowed to come into contact with any painted or plastic parts. It will quickly destroy both of these surfaces, and if accidentally splashed, should be washed off immediately. Remove the plastic caliper cover and the pads as described in Maintenance - Major service - 14.2: Check and renew the brake pads (disc brakes - front and rear).
  4. Remove the two socket screws which retain the caliper halves, to give access to each piston assembly. Remove the dust seal and withdraw the piston and seals from each side. If the pistons are difficult to extract, wrap the caliper in thick rag and apply compressed air to the fluid passage to force the pistons out. Examine all the components carefully. The seals should be renewed as a matter of course. The working surface of the piston should be highly polished with no scores or corroded areas. If these are evident, the piston must be renewed or it will rapidly destroy the new seals. The caliper bores are least likely to exhibit signs of wear or corrosion damage but if such evidence is present, it will necessitate renewal of the caliper body as a unit.
  5. The component parts should be cleaned thoroughly with new brake fluid prior to reassembly. On no account use petrol (gasoline) or paraffin (kerosene) as these will ruin the seals. Reassemble, by reversing the dismantling sequence, ensuring that all parts are kept clinically clean. Lubricate the seal and piston with hydraulic fluid prior to fitting them to the caliper. Make sure that the brake pipe is fitted correctly. Before using the machine, bleed the brake system. See Section 9 - Bleeding the hydraulic brake system.

Brake Caliper Rear
Rearbrake caliper