Recently I read a letter to the editor in a magazine pertaining to how an RV couple back up their towed vehicle by having one person steer the towed vehicle while the other backs up the motorhome. I feel a word of caution is in order here. Last summer we tried backing up several towed vehicles with a motorhome. While the motorhome backed up, I was in the towed vehicle steering it. The front tires suddenly whipped off to one side and the steering wheel violently spun out of control. It happened so fast my arms crossed up and hit each other and I was lucky I didn't break my thumb or arm. I would not recommend anyone try to "steer" the towed vehicle while backing. We did however have limited success backing in a straight line using our tow bar. The problem is that inevitably all vehicles we tried had the same thing happen to the front tires all at different intervals. We also tried other manufacturers tow bars with the exact same result.
The reason this happens is not the tow bar but rather the caster angle in the front end of the towed vehicle. Caster is the forward tilt of the steering axis versus vertical. It provides steering stability, steering returnability and cornering ease. In reverse, the caster angle makes the wheels want to turn around the other direction like "casters" on your office chair or shopping cart. We all know they can't turn all the way around on a car, but they will turn off to the side as far as the steering mechanism will let them. This is virtually undetectable from the driver's seat in the motorhome making this a very scary situation. If you continue to back up, after the wheels have turned, the tires "scrub" or slide sideways causing damage to the tires. Other things caused by this are; severe stress to the steering components, suspension and towing system components.
Another good example of caster at work is a bicycle. Nearly everyone in their younger days has ridden a bike down the street without holding onto the handlebars, but how many have done it going backwards? None with any success I would expect as the front tire tries to turn around the other direction causing…well...a crash. To be on the safe side, heed the warnings; don't back up with any tow bar.
