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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.
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