Inspection
1. Loosen the wheel nuts, raise the car on stands. Remove the wheels and install two nuts with 3mm washers to hold the disc in place. When inspecting the rear brake, release the parking brake.
2. Remove the caliper (see Section 3). It is not necessary to disconnect the brake hoses. Fasten the calipers away from the work area. Remove the two bolts securing the guide to the steering knuckle (see fig. 4.2a) or, on rear brakes, to the trunnion bracket (see fig. 4.26). take that bracket off.
Pic. 4.2a Bolts for fastening the bracket to the steering knuckle
Pic. 4.2b Bolts for fastening the bracket to the axle of the rear wheel
3. Inspect the disc for nicks and damage. Light scratches and shallow grooves are no cause for concern. If the grooves or scratches are deeper than 0.4 mm, resurfacing of the disc is required. Examine both sides of the disk.
4. If during braking there are pulsations of the braking force, check the runout of the disc. To do this, place the indicator leg at a distance of about 13 mm from the outer edge of the disc (see fig. 4.4a) Set the indicator to zero and spin the disc. The runout should not exceed the values given in the specification.
Pic. 4.4a Measuring with a disc runout indicator
Pic. 4.4b Preparing the disk surface for measurement
Note: To eliminate the influence of disc irregularities when measuring runout, smooth out the marks with sandpaper in a circular motion (see fig. 4.4b).
5. It is possible to machine the surface of the disk only up to certain limits: the minimum thickness of the disk is punched on its rim.
Pic. 4.5 Specifying the minimum disc thickness
Withdrawal
6. Loosen the retaining nuts (or retaining screws, see construction) and remove the disc from the hub. If the disc cannot be removed, screw the two bolts into the special threaded holes and remove the disc.
Pic. 4.6 Removing the disc using threaded holes
Installation
7. Slide the disc onto the studs.
8. Install the pad guide and caliper. Fasten the guide with the force given in the specification.
9. Lower the machine after installing the wheels first. Press the brake pedal several times to install the pads in place. Bleed, if necessary, the brake system.