This maintenance manual provides technical instructions for the service and repair of Meritor Wedge Brakes, specifically the Stopmaster models used in truck, tractor, and trailer applications. These brakes are available in various configurations, including 13-inch and 15-inch diameters, and are designed for air or hydraulic actuation .

1. Key Technical Specifications

Accurate technical settings are essential for effective braking and component longevity:

Brake Lining Wear Limits: Replace linings when the material is worn to 1/16-inch (1.5 mm) above the rivet heads or when the total thickness reaches the manufacturer’s minimum limit.
Drum Service Limits: A standard 15-inch drum must be replaced if worn or machined beyond a maximum diameter of 15.120 inches.
Lining-to-Drum Clearance: During initial adjustment, the clearance should be set by turning the adjusting bolt until the linings touch the drum and then backing off according to model-specific requirements.

2. Core Maintenance and Assembly

Lubrication: Critical internal components, such as the wedge head, plungers, and adjusting screws, must be lubricated with Meritor-approved grease (e.g., Mobilith SHC 460) during every major overhaul to ensure smooth operation.
Matched Components: Always install matched sets of linings on both ends of an axle to prevent uneven braking or pulling.
Cleaning: Ground and polished metal parts should be cleaned with a safe solvent like kerosene or diesel fuel; never use gasoline, water, or steam on these surfaces .

3. Safety Warnings

Dust Hazard: Do not use high-pressure air hoses or dry brushing to clean brake assemblies, as airborne dust—regardless of material type—may contain hazardous fibers.
Actuator Precautions: Never apply air or hydraulic pressure to a wedge actuator while it is disassembled, as internal parts can be ejected with sufficient force to cause serious injury.