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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 512 (Disc Brakes) >> Adjustments & Inspections >> Brake Rotor Assembled Lateral RUNOUT (LRO) Measurement

Brake Rotor Assembled Lateral RUNOUT (LRO) Measurement

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    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 3000-7000 mi (4828-11265 km).
    NOTE: 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. See BRAKE ROTOR THICKNESS MEASUREMENT .
  1. Matchmark the position of the brake rotor to the wheel studs if this has not been done already.
    2. NOTE: Whenever the brake rotor has been separated from the hub/axle flange, and 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 lateral runout (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. See BRAKE ROTOR  under REMOVAL & INSTALLATION.
    2. Using the Wheel Hub Resurfacing Kit (J-42450-A), thoroughly clean any rust or corrosion from the mating surface of the hub/axle flange.
    3. Using the Rotor Resurfacing Kit (J-41013), 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 Conical Brake Rotor Washers (J-45101-100), and one lug nut 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 Conical Brake Rotor Washers and lug nuts onto the wheel studs and tighten the nuts firmly by hand in a star-pattern.
  7. Using the Torque-Limiting Socket Set (J-39544-KIT), or equivalent, tighten the lug nuts in a star-pattern to specifications, in order to properly secure the rotor. See TORQUE SPECIFICATIONS .
  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, Hub And Wheel Runout Gage (J-45101), or equivalent, to the steering knuckle and position the indicator button so it contacts the brake rotor friction surface at a 90 degree angel, approximately 0.5" (13 mm) 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 locations 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 specifications. See LATERAL RUNOUT SPECIFICATIONS  table.
    LATERAL RUNOUT SPECIFICATIONS

    Application In. (mm)
    Front Brake Rotor Maximum Allowable Assembled Lateral Runout 0.002 (0.06)
    Rear Brake Rotor Maximum Allowable Assembled Lateral Runout 0.002 (0.06)
  13. If the brake rotor assembled LRO is within specifications, proceed to step  18. If the brake rotor assembled LRO exceeds the specification, refinish the rotor to ensure true parallelism. See BRAKE ROTOR REFINISHING . After refinishing the rotor, proceed to next step.
  14. Mount a dial indicator, Hub And Wheel Runout Gage, 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 0.5" (13 mm) from the outer edge of the rotor.
  15. Measure and record the assembled LRO of the brake rotor.
    • Rotate the rotor until the lowest reading is displayed on the indicator dial, then set the dial to zero.
    • Rotate the rotor until the highest reading is displayed on the dial.
    • Mark the location of the high spot relative to the nearest wheel stud, or studs.
    • Measure and record the amount of LRO.
  16. Compare the brake rotor assembled LRO to the following specifications. See LATERAL RUNOUT SPECIFICATIONS  table.
  17. If the brake rotor assembled LRO measurement exceeds the specifications, bring the LRO to within specifications. See BRAKE ROTOR ASSEMBLED LATERAL RUNOUT (LRO) CORRECTION .
  18. 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 Conical Brake Rotor Washer and the lug nuts.
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