Document 6B1JnONMwMYk4p90Q7w9VajN1

BRAKE SYSTEM DIAGNOSIS AND TESTING LESSON ONE-MODULE 1 COMMON CUSTOMER CONCERNS Brake Roughness Brake roughness is defined as vibration felt in the: seat steering wheel brake pedal during normal brake application. Normal Roughness Some customers may interpret normal ABS operation as a brake roughness symptom. Normal ABS operation includes: Pulsation in the brake pedal. This condition is normal, and indicates proper functioning of the vehicle's anti lock brake system (ABS). This pulsation is felt if traction is lost at one or more wheels while braking: - During panic conditions. - On loose gravel. - When the tires are unloaded on uneven road surfaces. - On a wet or snowy road. The ABS is releasing and reapplying the brakes to prevent wheel lock up. Abnormal Roughness Abnormal brake roughness may be caused by: Loose or missing wheel hub bolts. Damaged wheel bearings. Wheel or tire imbalance/uneven wear. Foreign materials, rust, or scratches on braking surfaces or wheel hubs. Damaged brake pads or shoes. Grease or fluid on pads or shoes. Poorly lubricated sliding parts. Lining material transfer. Brake rotor runout Wheel hub runout Disc thickness variation. Out-of-round brake drums. Uneven lug nut torque. Brake System Diagnosis and Repair September, 2005 9