Why does the big truck stop bleeding when it stops?

Answer:

Large buses and large trucks to the majority of pneumatic brake system, it works mainly use the gas tank of compressed air in the brake release the brake pedal, the brake system of pipeline valve open discharge the compressed air in the brake pipe, so the exhaust sound

You hear the sound of two kinds, one is for the parking brake, stop release will have the voice of deflation; one is some car parking brake and air brake, then pull the handbrake will put a part in gas.

The truck is a basic air brake, brake, brake pipe will go to inflation and push the brake pad and brake drum contact, achieve the braking effect, leave brake, brake for gas will be released, the brake release.