Document wDdoewYq9QkXyv0YNdJnLZNx3

BRAKE SYSTEM SERVICE LESSON ONE-MODULE 2 DRUM BRAKE INSPECTION AND LINING REPLACEMENT (continued) Duo-Servo vs. Leading-Trailing Brakes Item Description 1 Duo-Servo Brake Assembly Item Description 2 Leading-Trailing Brake Assembly Normal wear patterns on drum brakes will vary with the type of drum brake being inspected. On leading-trailing brakes the leading shoe performs the majority of the braking when the vehicle is moving forward. Therefore, the majority of the wear will be evident on the leading brake shoe. When inspecting duo-servo brakes, the secondary shoe performs the majority of the braking when the car is moving forward, due to the servo action. This means that the secondary shoe will be subject to the most wear. Keep these wear patterns in mind when inspecting drum brakes, and look for abnormal wear patterns. Abnormal wear patterns may give you a clue to the cause of a customer concern, or of a damaged brake drum. DRUM BRAKE LINING SERVICE Although specific procedures vary between vehicle and drum brake types, the following outlines the general sequence for servicing drum brakes. Remove wheel, brake drum and parts from the backing plate. Cleaning, inspecting, and replacing worn or damaged parts. Inspecting, measuring, and machining or replacing brake drums. Lubricating and reassembling brake parts. Pre-adjusting the brakes and reinstalling the brake drums and wheels. Brake System Diagnosis and Repair September, 2005 53