eli5 Why do trucks and busses do the “tsshhh” thing when they stop?
In: Engineering
Heavy duty vehicles have heavy duty brakes that function differently than normal cars and trucks. They use an air system to stop instead of regular pads and rotors or drums.
They also work backwards of a normal car. When you hit the brakes in a normal car they squeeze on the rotor slowing the car down. In a semi or a bus they pump air into the brakes to get them to release and when they hit the brakes it bleeds off this air pressure so the brakes will apply. When the vehicle comes to a complete stop the pshhh sound you hear is it just releasing the air so the brakes will reapply.
This is important for heavy duty vehicles because if their braking system fails they don’t have a vehicle that weighs 80,000 pounds screaming down the high way unable to stop. If it fails it just applies the brakes bringing it to a stop.
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