Freddy wrote:I guess I'm confused.... last I knew brakes on semi's are "on" unless the vehicle is running. How could this truck be free wheeling? I'm not a semi driver, but aren't I close to correct?
The brakes are independent of the truck other than the air compressor on the motor. They even have connectors on them so if you wanted charge it with an external compressor you can do that. I know at the fire station my brother works at they have them hooked to air whenever they are parked so they don't have to wait for the pressure to come up.
There is giant springs on the brakes, these are the parking/emergency brakes. When the system is charged with air you can then release the parking brake. If the system does not have enough pressure to operate properly you'll get a warning buzzer and if it continues to lose air the parking brake will engage automatically. In this case the system must of still had pressure and no one ever manually engaged the parking brake. Someone would of had to gone in the cab and pushed the button for the brake or bleed the air tanks.
As far as the video goes I'm surprised it was able to flip the wrecker over, must be steeper hill than it looks like.