Rotor Service

Tools Required:

• Rotunda Disc Brake Lathe 054-00080

Refer to Section 06-00 for Brake Diagnosis and to the information below for conditions requiring rotor refinishing.

Brake roughness (vibration or pedal pulsation) that is present during service brake application is caused by either rotor thickness variation or corrosion buildup on the rotor braking surfaces. This thickness variation can occur with rotor wear in excess of 19,311 km (12,000 mile) use. Rotor turning may thus be necessary beyond the warranty period. The rotors should only be turned as a last resort. The suspension and brake systems are designed and built to tolerate rotor thickness variations well above previous brake designs. Rotor replacement should only be required for such circumstances as damaged rotors, bearings or heavy rotor scoring where rotor turning is not possible.

If pedal pulsation occurs, attempt stopping the vehicle with the transmission in NEUTRAL. If roughness is gone, the drivetrain should be inspected. If the roughness remains, inspect the brakes. If corrosion buildup is the cause, hand sand the brake pads and rotor braking surfaces to remove the scale. If buildup is light, the condition should disappear after a few brake applications.

Use Rotunda Disc Brake Lathe 054-00080 or equivalent to refinish disc brake rotors.

To Check Rotor:

Rotor minimum thickness must not be less than 24.68mm (0.972 inch) on Mustang 5.0L, (20.5mm (0.81 inch) on Mustang 2.3L, nor less than the number cast on the inside of the rotor after refinishing. Lateral runout of the braking surfaces must not exceed 0.08mm (0.003 inch), and the surface finish is to be in the 15 to 125 micro-inch range.

1. Check the rotor for the maximum amount of stock that can be removed from the rotor thickness. Measure actual rotor thickness with micrometer and subtract minimum allowable thickness (cast in individual rotor). Total material removal (combination of both sides) must not exceed this amount.

   If the rotor thickness is less than the minimum the rotor must be replaced regardless of the disc rotor surface. Rotor minimum thickness is also shown on each rotor.

2. Position the rotor in the lathe arbor. Never use a lathe that cuts only one face of the rotor at a time; it must be a simultaneous straddle cut. Install a dial indicator to read rotor lateral runout near the center of the rotor face. If runout is 0.05mm (0.002 inch) or below, proceed to machine rotor.

   If runout is over 0.05mm (0.002-inch), loosen rotor on the arbor and rotate the rotor 90 degrees. Read the runout and if it is below 0.05mm (0.002 inch), proceed to machine the rotor. If runout is still over 0.05mm (0.002 inch), again loosen the rotor, and rotate it an additional 90 degrees. Check the runout. If runout is 0.05mm (0.002 inch) or less, proceed to machine the rotor. If the runout still exceeds 0.05mm (0.002 inch), return the rotor to the best runout position obtained. If the rotor runout can be brought below 0.13mm (0.005 inch), proceed to machine the rotor. If the rotor cannot be brought below 0.13mm (0.005 inch) runout, it must be replaced.

3. Set the cutting tool to just contact the high spots on the rotor, then adjust the cutting tool to the minimum depth required to clean up the rotor face.

   Before installing the rotor on the spindle, clean all chips from the rotor and flush new grease through the bearing with a bearing packing tool. A new inner grease retainer must be coated with wheel bearing grease and installed in the rotor. The rotor must be installed on the same side of the vehicle from which it was removed.