How much pressure should you apply to the foot valve when measuring slack adjustment?

When measuring slack adjustment in a braking system, a full brake application is essential for accurate readings. This is because a complete application ensures that all components of the braking system, including the slack adjusters, are fully engaged. By applying full pressure, you can assess whether the slack adjusters are functioning correctly and whether the brakes are properly adjusted.

Accurate slack adjustment is critical for safe vehicle operation, especially for heavy trailers, as it prevents excessive brake wear and maintains optimal braking performance. When the brakes are fully applied, it gives a clear indication of how much movement is allowed in the slack adjusters, enabling proper assessments and necessary adjustments to be made. This process is important not only for vehicle safety but also for compliance with regulations governing heavy trailers.