eli5 Why do trucks and busses do the “tsshhh” thing when they stop?

Question

eli5 Why do trucks and busses do the “tsshhh” thing when they stop?

In: Engineering

Answer 1

The bus uses a lot of air to hold the brakes up. <**Breath in while holding the kid up**> So when they need to park, they release all that air! <**Blow out of your mouth while slowly putting the kid down**>

Our car doesn’t do this because we don’t use compressed air in our cars (we use a really cool oil network instead but that isn’t suitable for a bus of this size).