Brake Rotor/Disc

BRAKE ROTOR/DISC Front Disc Brake Rotor Diameter - 16 in. Wheels 302 mm (11.89 in.) Front Disc Brake Rotor Diameter - 17 in. Wheels 332 mm (13.07 in.) Rear Disc Brake Rotor Diameter 316 mm (12.44 in.) Front Ventilated Disc Brake Rotor Max. Runout 0.020 mm (0.0008 in) Rear Solid Disc Brake Rotor Max. Runout 0.020 mm (0.0008 in) Front Ventilated Disc Brake Rotor Max. Thickness Variation 0.009 mm (0.00035 in.) Rear Solid Disc Brake Rotor Max. Thickness Variation 0.009 mm (0.00035 in.) Front Ventilated Disc Brake Rotor Min. Thickness 26.4 mm (1.049 in.) Rear Solid Disc Brake Rotor Min. Thickness 10.4 mm (0.409 in.)

ROTOR RESURFACING The disc brake rotor can be machined if scored or worn. The on-vehicle lathe must machine both sides of the rotor simultaneously with dual cutter heads. The rotor mounting surface must be clean before placing on the on-vehicle lathe. Equipment capable of machining only one side at a time may produce a tapered rotor. This type of rotor machining is not recommended.

BRAKE DRUM IN HAT ROTOR MACHINING The brake drum in hat rotor can be machined on a drum lathe when necessary. Initial machining cuts should be limited to 0.12 - 0.20 mm (0.005 - 0.008 in.) at a time as heavier feed rates can produce taper and surface variation. Final finish cuts of 0.025 to 0.038 mm (0.001 to 0.0015 in.) are recommended and will generally provide the best surface finish. Be sure the drum in hat rotor is securely mounted in the lathe before machining operations. A damper strap should always be used around the drum to reduce vibration and avoid chatter marks. The maximum allowable diameter of the drum braking surface is stamped or cast into the drum in hat rotor.

DISC BRAKE ROTOR Special Tools: The rotor braking surfaces should not be refinished unless necessary. Light surface rust and scale can be removed with a lathe equipped with dual sanding discs. The rotor surfaces can be restored by machining in a disc brake lathe if surface scoring and wear are light. Replace the rotor under the following conditions: -severely scored -tapered -hard spots -cracked -below minimum thickness ROTOR MINIMUM THICKNESS Measure rotor thickness at the center of the brake shoe contact surface. Replace the rotor if worn below minimum thickness, or if machining would reduce thickness below the allowable minimum. Rotor minimum thickness is usually specified on the rotor hub. The specification is either stamped or cast into the hub surface. ROTOR RUNOUT Check rotor lateral runout with dial indicator (1) (Figure 1). Excessive lateral runout will cause brake pedal pulsation and rapid, uneven wear of the brake shoes. Position the dial indicator plunger approximately 25.4 mm (1 in.) inward from the rotor edge. The dial indicator should be positioned in the center of the rotor surface. Maximum allowable rotor runout is 0.102 mm (0.004 in.). ROTOR THICKNESS VARIATION Variations in rotor thickness will cause pedal pulsation, noise and shudder. Measure rotor thickness at 6 to 12 points around the rotor face (Figure 2). Position the micrometer (1) approximately 25.4 mm (1 in.) from the rotor (2) outer circumference for each measurement. Thickness should not vary by more than 0.013 mm (0.0005 in.) from point-to-point on the rotor. Machine or replace the rotor if necessary.

The maximum allowable diameter of the drum braking surface is indicated on the drum outer edge. Always replace the drum if machining would cause drum diameter to exceed the size limit indicated on the drum in hat.

Measure drum diameter and runout with an accurate gauge. The most accurate method of measurement involves mounting the drum in a brake lathe and checking variation and runout with a dial indicator.

Machine the drum if runout or variation exceed values. Replace the drum in hat rotor if machining causes the drum in hat rotor to exceed the maximum allowable diameter.

The rotor braking surfaces should not be refinished unless necessary.

Light surface rust and scale can be removed with a lathe equipped with dual sanding discs. The rotor surfaces can be restored by machining in a disc brake lathe if surface scoring and wear are light.

Replace the rotor under the following conditions:

severely scored tapered hard spots cracked below minimum thickness

Measure rotor thickness at the center of the brake shoe contact surface. Replace the rotor if worn below minimum thickness, or if machining would reduce thickness below the allowable minimum.

Rotor minimum thickness is usually specified on the rotor hub. The specification is either stamped or cast into the hub surface.

1 - DIAL INDICATOR

Check rotor lateral runout with dial indicator C-3339 (1). See Fig. 35. Excessive lateral runout will cause brake pedal pulsation and rapid, uneven wear of the brake shoes. Position the dial indicator plunger approximately 25.4 mm (1 in.) inward from the rotor edge. The dial indicator should be positioned in the center of the rotor surface. Maximum allowable rotor runout is 0.102 mm (0.004 in.).

1 - MICROMETER 2 - ROTOR

Variations in rotor thickness will cause pedal pulsation, noise and shudder.

Measure rotor thickness at 6 to 12 points around the rotor face. See Fig. 36.

Position the micrometer (1) approximately 25.4 mm (1 in.) from the rotor (2) outer circumference for each measurement.

Thickness should not vary by more than 0.013 mm (0.0005 in.) from point-to-point on the rotor. Machine or replace the rotor if necessary.

The brake drum in hat rotor can be machined on a drum lathe when necessary. Initial machining cuts should be limited to 0.12 - 0.20 mm (0.005 - 0.008 in.) at a time as heavier feed rates can produce taper and surface variation. Final finish cuts of 0.025 to 0.038 mm (0.001 to 0.0015 in.) are recommended and will generally provide the best surface finish.

Be sure the drum in hat rotor is securely mounted in the lathe before machining operations. A damper strap should always be used around the drum to reduce vibration and avoid chatter marks.

The maximum allowable diameter of the drum braking surface is stamped or cast into the drum in hat rotor.

CAUTION: Replace the drum in hat rotor if machining will cause the drum to exceed the maximum allowable diameter.

NOTE: A hub mounted on-vehicle lathe is highly recommended. This type of lathe trues the rotor to the vehicles hub/bearing.

The disc brake rotor can be machined if scored or worn. The on-vehicle lathe must machine both sides of the rotor simultaneously with dual cutter heads. The rotor mounting surface must be clean before placing on the on- vehicle lathe. Equipment capable of machining only one side at a time may produce a tapered rotor. This type of rotor machining is not recommended .

NOTE: Proper wheel torque is also critical to help prevent any warping of the disc brake rotor.

CAUTION: Brake rotors that do not meet minimum thickness specifications before or after machining must be replaced.

1. Raise and support the vehicle. 2. Remove the tire and wheel assembly.

CAUTION: Never allow the disc brake caliper to hang from the brake hose. Damage to the brake hose will result. Provide a suitable support to hang the caliper securely.

3. Remove the caliper adapter (2). See REMOVAL. 4. Remove the disc brake rotor (3).

1. Install the disc brake rotor (3) to the hub. 2. Install the caliper mounting adapter (2). See INSTALLATION. 3. Install the tire and wheel assembly. Refer to STANDARD PROCEDURE .

1.   Install the rotor (1) to the axle shaft.
  2.   Install the disc brake caliper adapter (2) and pads (3). See INSTALLATION.
  3.   Install the tire and wheel assembly. Refer to STANDARD PROCEDURE .
  4.   Lower the vehicle.

PEDAL