The brake system should not be interfered with by anybody who does not have the appropriate skills and experience. Brake pads should be replaced by a qualified mechanic. These are general instructions, for the assistance of experienced technicians. For more detailed instructions pertaining to a specific vehicle on how to fit brake pads, consult the manufacturer’s service manual. Approved safety equipment should be used at all times. Use the correct tools for each task. Before starting work, ensure these instructions have been read and understood completely.
1. Raise the vehicle off the ground and remove the wheels. If a vehicle hoist is not available, ensure the wheels are chocked and the vehicle is supported by chassis stands on level ground. Do not work under a car supported only by a jack.
2. Inspect the caliper for wet patches which may indicate a brake fluid leak. Clean the brake with brake and parts cleaner. Do not use compressed air, dry brushing, oil-based or petroleum-based solvents.
3. Remove the brake pads from the caliper. The procedure varies greatly depending on the type of caliper. It may be helpful to work on one brake at a time, leaving the opposite brake assembled as a reference. Unplug any electronic pad wear indicators before starting.
a. Sliding calipers:
1. Some sliding caliper designs allow the caliper body to pivot on the upper slide pin when the bolt is removed from the lower slide pin. Swing the caliper body away from the anchor bracket to provide access to the pads. Take care not to damage the flexible brake hose.
2. Some sliding caliper designs require the bolts to be removed from both slide pins, and the caliper body lifted away from the anchor bracket to provide access to the brake pads.
3. Some sliding caliper designs do not use a separate anchor bracket, with slide pins mounted to the suspension knuckle. Remove the caliper body from the suspension knuckle, or pivot the caliper body around the upper slide pin, to provide access to the pads.
4. Some sliding caliper designs use pins and clips to hold the caliper body to the anchor bracket. Refer to manufacturer’s instructions for disassembling these calipers if necessary.
5. The pads may be secured in the caliper body using clips or springs, or may be captive in the anchor bracket. Take note of the arrangement of clips when disassembling the caliper to remove the pads. Springs may be under tension, and require care to disassemble safely.
b. Opposed-piston calipers:
1. Most opposed-piston caliper designs have a window in the bridge of the caliper to allow access to the pads. The pads are typically located in the caliper using pins and clips. Remove any pins or clips and withdraw the pads through the window.
2. Some opposed-piston caliper designs require the caliper to be removed from the suspension knuckle to provide access to the pads.
c. Other caliper designs:
1. For other caliper designs, consult manufacturer’s instructions.
4. Remove the caliper from the suspension knuckle (if it was not completely removed during step 3), taking care not to damage the flexible brake hose. Secure the caliper to the vehicle, in a convenient position that does not put undue stress on the brake hose.
5. Inspect the condition of the used pads. If the pads show uneven wear, the caliper may need to be overhauled or replaced. Refer to local regulations for disposal of used brake pads.
6. Inspect the condition of the caliper. Ensure all dust boots, caps and seals are in good condition, and that sliding surfaces are not damaged. For sliding calipers, lubricate the slide pins and ensure they are straight, in good condition, and allow the caliper to slide freely. Check that the brake hose is in good condition. Replace any component that shows signs of damage or deterioration. If the caliper uses a stepped piston design, ensure the orientation of the step is correct according to the manufacturer’s instructions.
7.Rotors should be machined if they are to be re-used. Use a micrometer to measure the thickness of the rotor at several radii across the face. The minimum thickness is marked on the rotor. If a rotor is under minimum thickness (or will be under minimum thickness after machining), or if it is tapered, replace the pair of rotors. If on-vehicle machining is not possible, of if the rotor is to be replaced, remove the brake rotor from the vehicle following the manufacturer’s instructions.
If wheel bearings are integral to the rotor and are to be replaced, it should be done before machining. Machine the rotor using the slowest feed rate. Do not take heavy cuts. The final cut should be very light to minimise grooving of the braking surface. After machining, finish both braking surfaces of the rotor with 240 grit emery to obtain a smooth non-directional surface finish. Clean the rotor with brake and parts cleaner. If the rotor was removed from the vehicle, re-fit the rotor following the manufacturer’s instructions.
8. Use a dial gauge to measure installed rotor run-out. If the rotor is the type that is located and held in place by the wheel, use the wheel nuts to temporarily locate the rotor on the hub. Installed rotor run-out should not exceed 100µm (0.1mm). If acceptable run-out cannot be achieved, further investigation is required. The rotor, hub or suspension components may be damaged.
9. Mount the anchor bracket (for sliding calipers) or the caliper body (for opposed-piston calipers) on the suspension knuckle. Tighten the bolts to the manufacturer’s recommended torque. Note: if the caliper requires pads to be fitted before caliper installation, complete steps 10-11 before mounting the caliper.
10. Clamp the brake hose and open the bleed screw on the caliper. Use a bleed hose to catch excess brake fluid in a suitable container as you push the pistons back into the caliper. Pistons should be pushed back by hand or using a piston retraction tool. Ensure all pistons can move without binding. Take care not to expose skin, clothing or paintwork to brake fluid.
Calipers with an integral park brake often require an alternate method to retract the piston. Consult the manufacturer’s instructions.
11. Fit the new brake pads to the caliper body or anchor bracket and reassemble the caliper. For sliding calipers, fasten the caliper body to the anchor bracket and tighten all bolts to the manufacturer’s recommended torque. Ensure all clips, pins etc. are correctly installed.
12. Complete pad change and inspection of all brakes.
13. Flush and replace the brake fluid, unless service records show that it has been replaced within the last 12 months. Brake fluid should be flushed and replaced at least once every two years, as it absorbs water from the atmosphere which reduces its performance. Refer to the vehicle manufacturer’s recommendation for the correct specification of brake fluid.
To avoid contamination of the brake fluid, clean the master cylinder reservoir with brake and parts cleaner before opening. Add new brake fluid to the reservoir as required, from a fresh sealed container. Flush new brake fluid through the entire brake system, starting at the wheel furthest from the master cylinder. Collect the used brake fluid in a suitable container. Refer to local regulations for disposal of used brake fluid.
14. Bleed the brakes following the manufacturer’s recommended procedure, paying attention to the appropriate bleeding order.
15. Apply the brakes several times to set the brake pads and pistons in position. Top up the brake fluid reservoir if necessary. If the brake pedal does not feel firm under foot, repeat step 14. Attach and adjust the park brake according to the manufacturer’s instructions. Wipe rotors down again with brake and parts cleaner.
16. Fit the wheels, lower the vehicle to the ground and tighten the wheel nuts to the manufacturer’s recommended torque.
17. Test drive the vehicle to ensure correct brake operation.
18. Follow the appropriate bed-in procedure for the brake pads fitted.
19. The brake system should be inspected by a qualified mechanic at least once per year, or more often if the vehicle travels long distances or is subject to heavy duty conditions.