Buick Regal: Brake Rotor Assembled Lateral Runout Measurement

Special Tools

GE-571-B Hub and Wheel Runout Gauge

For equivalent regional tools, refer to Special Tools.

WARNING: Refer to Brake Dust Warning.

NOTE:

• Brake rotor assembled lateral runout (LRO) exceeding the maximum allowable specification can cause thickness variation to develop in the brake rotor over time, usually between 4 800 - 11 300 km (3, 000 - 7, 000 mi).
• Brake rotor thickness variation MUST be checked BEFORE checking for assembled lateral runout (LRO). Thickness variation exceeding the maximum acceptable level can cause brake pulsation. Refer to Brake Rotor Thickness Variation Measurement.

1. Matchmark the position of the brake rotor to the wheel studs if this has not been done already.

NOTE: Whenever the brake rotor has been separated from the hub/axle flange, any rust or contaminants should be cleaned from the hub/axle flange and the brake rotor mating surfaces. Failure to do this may result in excessive assembled LRO of the brake rotor, which could lead to brake pulsation.

2. Inspect the mating surface of the hub/axle flange and the brake rotor to ensure that there are no foreign particles, corrosion, rust, or debris remaining. If the wheel hub/axle flange and/or if the brake rotor mating surfaces exhibit these conditions, perform the following steps:

1. Remove the brake rotor from the vehicle. Refer to Front Brake Rotor Replacement (JQ5)Front Brake Rotor Replacement (J17, J60), and/or Rear Brake Rotor Replacement, if equipped.
2. Thoroughly clean any rust or corrosion from the mating surface of the hub/axle flange.
3. Thoroughly clean any rust or corrosion from the mating surface of the brake rotor.
4. Clean the friction surfaces of the brake rotor with denatured alcohol, or an equivalent approved brake cleaner.

3. Install the rotor to the hub/axle flange using the matchmark made prior to removal.

4.

Hold the rotor firmly in place against the hub/axle flange and install one of the lug nuts (2) onto the upper-most wheel stud.

5. Continue to hold the rotor secure and tighten the lug nut firmly by hand.

6.

Install the remaining lug nuts onto the wheel studs and tighten the nuts firmly by hand in a star-pattern.

7. Tighten the lug nuts in a star-pattern to specification, in order to properly secure the rotor. Refer to Tire and Wheel Removal and Installation.

8. If the brake rotor has been REFINISHED or REPLACED with a new rotor, proceed to step 14.

9. If the brake rotor meets the following criteria, proceed to step 10.

• The rotor is within specifications and is being REUSED
• The rotor has NOT been refinished
• The rotor does NOT exhibit thickness variation exceeding the maximum allowable level

10.

Mount a dial indicator, GE-571-B Hub and Wheel Runout Gauge, or equivalent, to the steering knuckle and position the indicator button so it contacts the brake rotor friction surface at a 90 degree angle, approximately 13 mm (0.5 in) from the outer edge of the rotor.

11. Measure and record the assembled LRO of the brake rotor.

1. Rotate the rotor until the lowest reading is displayed on the indicator dial, then set the dial to zero.
2. Rotate the rotor until the highest reading is displayed on the dial.
3. Mark the location of the high spot relative to the nearest wheel stud, or studs.
4. Measure and record the amount of LRO.

12. Compare the brake rotor assembled LRO to the following specification:

Specification

• Front brake rotor maximum allowable assembled lateral runout: 0.10 mm (0.004 in)
• Rear brake rotor maximum allowable assembled lateral runout: 0.10 mm (0.004 in)

13. Mount a dial indicator, GE-571-B Hub and Wheel Runout Gauge, or equivalent, to the steering knuckle and position the indicator button so it contacts the brake rotor friction surface at a 90 degree angle, approximately 13 mm (0.5 in) from the outer edge of the rotor.

14. Measure and record the assembled LRO of the brake rotor.

1. Rotate the rotor until the lowest reading is displayed on the indicator dial, then set the dial to zero.
2. Rotate the rotor until the highest reading is displayed on the dial.
3. Mark the location of the high spot relative to the nearest wheel stud, or studs.
4. Measure and record the amount of LRO.

15. Compare the brake rotor assembled LRO to the following specification:

Specification

• Front brake rotor maximum allowable assembled lateral runout: 0.10 mm (0.004 in)
• Rear brake rotor maximum allowable assembled lateral runout: 0.10 mm (0.004 in)

16. If the brake rotor assembled LRO measurement exceeds the specification, bring the LRO to within specifications.

17. If the brake rotor assembled LRO measurement is within specification, install the brake caliper and depress the brake pedal several times to secure the rotor in place before removing the lug nuts.

BRAKE PAD INSPECTION

Special Tools

CH-230-A Disc Gauge

For equivalent regional tools, refer to Special Tools.

WARNING: Refer to Brake Dust Warning.

1. Remove brake pads. Refer to Front Disc Brake Pads Replacement (J60)Front Disc Brake Pads Replacement (JQ5)Front Disc Brake Pads Replacement (J17), and/or Rear Disc Brake Pads Replacement (GNC)Rear Disc Brake Pads Replacement (GNQ).

2.

Measure remaining brake pad thickness at several points, using the CH-230-A disc gauge (1).

3. Compare brake pad thickness to disc brake component specifications.

BRAKE CALIPER INSPECTION

1.

Inspect the brake caliper housing (1) for cracks, excess wear, and/or damage. If any of these conditions are present, the brake caliper requires replacement.

2. Inspect the caliper piston dust boot seal (6) for cracks, tears, cuts, deterioration and/or improper seating in the caliper body. If any of these conditions are present, the brake caliper requires overhaul or replacement.

3. Renew brake caliper bleeder valve cap (3) if missing.

4. Check for blocked bleeder valve (2).

5.

Inspect for smooth and complete travel of the caliper pistons into the caliper bores: The movement of the caliper pistons into the caliper bores should be smooth and even. If the caliper piston is frozen or difficult to bottom, the caliper requires overhaul or replacement.

Insert a discarded inner brake pad (2) or block of wood in front of the piston. Using a large C-clamp (1) installed over the body of the caliper (3) and against the brake pad or block of wood, slowly bottom the piston in the bore.

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