I am a trucker. I pull 53' dry van trailers with a big rig truck (a tractor). When a tractor-trailer backs straight backwards (not turning ) it is called straight line backing. Probably most people here know from backing boat trailers or other trailers at some point in their lives that when backing a trailer, if you turn the steering wheel to the left, it will make the rear of your trailer go to the right and if you turn steering wheel to the right, it will make the rear of the trailer go towards the left. Both the trucking school i attended and the trucking company i now work for told me that when a tractor-trailer is doing straight line backing, if the truck driver turns the steering wheel to the left or the right, the trailer will not respond by going the opposite direction until the tractor has backed up around 10 feet. To me, this seems counterintuitive and also potentially false. The tractor is connected to the trailer at the fifth wheel of the tractor. The trailer has a cylindrical bolt hanging down from the front of the trailer called a kingpin. The fifth wheel of the tractor has locking jaws that lock around the kingpin. The connection between the fifth wheel and the kingpin is a rigid connection. To me, it seems like since the connection between the fifth wheel and the kingpin is a rigid connection, that should mean that the trailer will react to the driver's turning the steering wheel (during straight line backing) IMMEDIATELY. Maybe the trailer's reacting to the driver's turning the steering wheel might be too subtle to detect until the tractor has backed ten feet, but it seems to me that the trailer's reacting to the driver's turning the steering wheel should happen when the tractor has moved just one foot. The instructors at my truck driving school said that when a trucker is doing straight line backing, the trailer won't react to the driver's turning the steering wheel until the tractor has backed 10 feet b/c the circumference of the wheel on the tractor-trailer is ten feet. I don't see how the circumference of the wheels could determine when the trailer reacts to when the driver turns the steering wheel. Are the instructors at my truck driving school and at my trucking company correct that the trailer will not react to the driver's turning the streering wheel until the tractor has backed 10 feet? Please explain.