Contents: Measures to eliminate brake judder ⇓ Checking the axial runout of the…⇓ Checking the unevenness of the brake…⇓ Checking the thickness of the brake…⇓ Checking the thickness of brake pads ⇓
Measures to eliminate brake judder
Shocks in the brake mechanisms appear in three forms:
- The steering wheel vibrates in the direction of the turn. This is most noticeable when applying the brakes at vehicle speeds of 100-140 km/h.
- When the brakes are applied, the car body sways back and forth. The degree of swaying does not depend on the speed of the car.
- When the brakes are applied, pulsating forces tend to push the brake pads back. This pulsation is transmitted to the brake pedal.
The most likely causes of brake pulsation are:
Excessive beating (wobble from side to side) brake disc, uneven thickness of brake disc
The original article is posted on Mazbook
- If the runout exceeds 0.04 mm at a distance of 10 mm from the edge of the brake disc, this indicates uneven wear of the brake disc due to uneven contact of the brake pads.
- If the runout is less than 0.04 mm, uneven wear does not occur.
Thermal deformation of the brake disc
- Repeated emergency braking can increase the temperature in some areas of the brake disc to approximately 1000°C, causing the brake disc to deform.
Due to corrosion, the thickness and friction coefficient of the brake disc change
- If the vehicle is left parked on a slope for a long time, the working surfaces of the brake disc are subject to corrosion.
- The thickness of the corrosion is uneven and in some places the disk has a wavy surface, as a result of which the adhesion coefficient changes, causing the appearance of reactive forces.
Checking the axial runout of the brake disc
1. To secure the brake disc to the hub, insert the washer (thickness 10 mm, internal diameter not less than 12 mm) between all the bolts and nuts of the hub, then tighten all the nuts of the hub.
Note: Components of special equipment (49 8017 001 or 49 G019 003) can be used as suitable nuts.
2. After tightening all hub nuts to the same torque, place a dial indicator on the working surface of the brake disc 10 mm from the outer edge of the disc.
3. Rotate the brake disc and measure the axial runout.
Note: Maximum permissible runout of the front brake disc: 0.04 mm.
Checking the unevenness of the brake disc thickness
1. Using a special cleaning agent, clean the friction surfaces of the brake disc/brake pads.
2. Using a caliper (micrometer) measure the brake disc at the points shown in the figure.
3. Subtract the minimum value from the maximum and, if the result does not correspond to the norm (0.015 mm), grind the brake disc using a special milling machine.
Caution: Do not exceed the maximum permissible minimum size of the brake disc.
Checking the thickness of the brake disc
Attention. Turning the brake disc with its removal from the car may cause its increased wear in the future. Turn the brake disc without removing it from the car using a special milling machine.
Measure the thickness of the brake disc. If the measured value is not within the norm, replace the brake disc with a new one.
Note:
- Minimum brake disc thickness: 26.0 mm.
- Minimum thickness of the brake disc after turning: 26.8 mm.
Checking the thickness of brake pads
1. Raise the front of the vehicle with a jack and install support stands.
2. Remove the front wheels from the vehicle.
3. Check the remaining thickness of the brake shoe linings.
Note: Minimum brake shoe lining thickness: 2.0 mm.
4. If the thickness of at least one of the brake linings is less than the minimum, replace the brake pads of the right and left wheels as one set.
