What psi should drum brakes be at when applied?

Drum brakes, particularly in firefighting and emergency vehicles, generally require a specific air pressure range to function effectively. When applied, the ideal psi for drum brakes is around 90 psi. This pressure ensures that the brakes engage properly and provide the necessary stopping power without causing excessive wear or potential failure of the braking system.

Operating at 90 psi allows for adequate force to compress the brake components, ensuring optimal contact with the brake drum for effective braking. Any significant deviation from this pressure can either lead to inadequate braking performance or unnecessary stress on the system, which can compromise safety.

Understanding this psi standard is critical for maintaining the operational integrity of the vehicle's braking system, ensuring it functions effectively in emergencies.