They don't need to do the revvin because of this reason because, at stop when the air is fully discharged, there si some sort of a spring mechanism to lock the brakes.
they need to rev up at start so that to build air pressure against the spring thingy.
Quote:
Originally Posted by Sideways  To answer your question specifically - Most truck and buses have air brakes. This air is stored in a tank and needs to be charged and therefore these guys rev the engines before they stop and just after they start so that they have some kind of braking power. The rest of it is hogwash. |