Note 1. Please read the note at the beginning before operation paragraph 4 about the dangers of asbestos dust.
Note 2: If one of the discs needs to be replaced, replace BOTH discs at the same time to ensure even and stable braking. Replace the brake pads as well.
Examination
1. Apply the parking brake, then raise the front of the car and place it on stands (cm. "Lifting and placing the car on supports"). Remove the corresponding front wheel.
2. Slowly turn the disc and inspect both sides of the disc. In order to better view the inner surface, remove the brake pads (see paragraph 4). Small scratches are allowed on the surfaces of the disc in contact with the pads. If there are deep scratches, scuffs, and cracks, the disc must be replaced.
3. On the periphery of the disc, the presence of a border of rust and dust from wear of the pads is allowed. If necessary, all this can be scraped off. If such a border is formed due to excessive development of the disc pad, then the thickness of the disc must be measured with a micrometer (pic. 6.3). Measure the thickness of the disc in several places along the inner and outer sliding radius of the pad. If in one of the places the thickness of the disk is at the limit (regulated "technical data" or below it) then the disk needs to be replaced.
4. If you are not sure about the flatness of the disk, then check the end runout. Measure the runout of the disc with a dial indicator fixed to some fixed part, slowly turning the disc. Alternatively, measure the gap between the disc and some fixed part. e.g. caliper support bracket, using flat feeler gauges. If the disc beat is at its limit (regulated technical data or above it), then the disc most likely needs to be replaced, although first you need to make sure that the hub bearing is in good condition (see chapter 10). If there is excessive runout, the disc must be replaced.
5. Inspect the rim for cracks, especially around the wheel bolt holes, and for wear or damage. Replace disk if necessary.
Withdrawal
6. Turn away two bolts of fastening of a basic arm of a support to a rotary fist. Then remove the caliper. Tie the caliper to the front suspension strut with wire or twine, being careful not to stretch the brake hose.
7. Mark the position of the disc relative to the hub, then unscrew the screw that secures the disc to the hub and remove the disc (pic. 6.7, a, b). If the disc does not come off, tap on the back of the disc with a plastic mallet.
Installation
8. Installation is made in sequence, return to removal. Pay attention to the following when assembling.
- A) Clean the mating surfaces of the disc and hub from dirt.
- b) Align the marks made before removal, then screw in and tighten the disc fixing screw to the required torque.
- V) Before installing a new disc, clean the disc of preservative with a suitable solvent.
- G) Put a caliper on the disc. Make sure the pads are in the correct position relative to the disc. Tighten the caliper mounting bolts to the required torque.
- d) Install the wheels, lower the vehicle to the ground and tighten the wheel bolts to the specified torque. At the end of work, press the brake pedal several times so that the pads approach the disc.