What is the best way to test if your vehicle's spring brakes come on automatically?
Answer: On tractor-trailer vehicles, continue to step on and off the brake pedal until the parking brake valve pops out, continue to step on and off the brake pedal until the manufacture's low psi specification has been met for spring brakes to deploy, on single vehicles, continue to step on and off the brake pedal until the parking brake valve pops out
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