Document wDONkp72gYLZ1Z59ndbJD23v6

BRAKE SYSTEM SERVICE Rotor Thickness and Thickness Variation LESSON ONE-MODULE 2 Every Rotor has a minimum allowable thickness. Rotor thickness ensures that the rotor is thick enough to dissipate heat, and not catastrophically fail during use. Ford rotors have the minimum thickness stamped into them, or the minimum thickness specifications are designated in the Workshop Manual. Discard any rotor that does not meet thickness specifications. Additionally, the inner and outer surfaces of the rotor must be parallel to each other. Stated another way, there must not be any disc thickness variation. Disc thickness variation is the primary cause of pedal pulsation, vibra tion, and brake shudder. Both these specifications can be checked at the same time using a micrometer. Measure the rotor at eight positions 45 degrees apart about 25.4 mm (1 in) in from the outside diameter of the rotor. If the thickness varies by more than .025 mm (.001 in) than the rotor must be machined or replaced with a new one. If any measurement is below the minimum thickness, or if machining the rotor will cause its thickness to be below minimum specifications, the rotor must be replaced. Brake System Diagnosis and Repair September, 2005 41