Remove the wheel.
Remove the brake caliper assembly.
Important! There is no need to remove the caliper from the vehicle, so after removing the caliper mounting bolts, secure it to the suspension strut with twine or wire. Do not hang the caliper on the brake hose as this may cause damage to the hose.
Caution: If a brake disc needs to be replaced, replace both to ensure uniform braking. When replacing brake discs, it is necessary to replace the brake pads as well.
Slowly turn the brake disc and visually inspect its condition on both sides. Brake disc wear from the pads must be within acceptable limits. If there are cracks on the disc, replace the disc.
Figure 10.5. Using a dial indicator to measure brake disc runout
Use a dial indicator to check the brake disc runout (figure 10.5). Attach the indicator to any convenient location and, by rotating the brake disc, determine its runout at a small distance from the outer edge. Before checking the brake disc runout, make sure the wheel bearing is in good technical condition. If the runout exceeds the maximum allowable and the bearing is in good condition, remove and regrind the brake disc. Some shops can resurface a brake disc without removing it from the vehicle.
Check the brake disc for cracks, especially around the wheel bolt holes, and for wear or mechanical damage; replace if necessary.
Measure the thickness of the brake disc at several points. Since there is a step around the perimeter of the brake disc, when measuring the thickness of the brake disc using a caliper, place two coins under its jaws. To determine the true thickness of the brake disc, subtract the thickness of two coins from the caliper reading.
Figure 10.6. Measuring brake disc thickness using a micrometer
A more accurate way to measure the thickness of a brake disc is to use a micrometer (figure 10.6).
If the thickness variations of the brake disc exceed 0.127 mm, pulsation may occur during braking. If the brake disc thickness is still sufficient, remove and regrind the brake disc.
Removing the brake disc from the hub requires the use of special tools and techniques, so it is necessary to remove the hub with the brake disc and deliver it to a service station for processing or replacement.