The spring brakes works like this: The pressure is applied to the spring side, which allows the parking brake to disengage. When the spring is decompressed (at 20 lbs), parking brakes have been applied. Air pressure hold back the the springs when you are driving. In this system, a leak is lowering air pressure and causes springs to engage the brakes.
Important to remember: Due the lack of braking power of the full service brake application, vehicles can be driven with spring brakes applied. Therefore, to avoid this situation, ensure that brake system has enough air pressure – 60 psi.
This system was firstly implemented for safety concerns, because trucks that had lost air pressure would struggle to reach controlled stop. So how did spring brake solve the problem?
Basically, the driver have more time, because the spring decompresses as the air pressure drops. Alarm is triggered whenever the pressure drops below the 60 lbs.
There are two chambers in spring brakes. One release spring, while other apply braking power. The spring is strong enough which means, that in case of sudden loss of pressure, it will apply full braking power to the axle and keep vehicle under control.
