Re: [VAC] Tandom vs. single axle

[Kevin Allen <kallen@xxxxxxxxxxxx>]

Greetings John!

I suspect that there were at least three reasons that Airstream switched to
tandem axles in their 22' to 26' units:

1.)  Competitive pressures.  As the industry adopted tandem axles for trailers
in similar size classes, it became important to be able to field a competitive
product for potential buyers who demanded tandem axles.

2.)  Increased weight of the trailers over time.  As trailer weights increased
due to higher levels of standard and optional equipment as well as customer
expectations for payload capacity - - it became increasingly difficult to build
a single axle trailer that would not overload the running gear.

3.)  Evolution of Tow Vehicles and safety regulations.  While the government
may never have regulated weights where tandem axles were required, there were
(and are) potential liability concerns for manufacturers who knowingly sell a
trailer that is likely to overload its running gear.  In addition, beginning in
the 1970s and beyond, there was a tremendous change in tow vehicles including
such things as weight, power, and physical size.  There was a time in the late
1970s through the early 1980s where lighter, less powerful autos were promoted
as being able to tow 3,000 to 5,000 pound trailers where the trailer outweighed
the car by as much as 1,000 pounds or more - - I owned one of those cars (1984
- ordered new with complete factory heavy duty trailer towing package) and a
3,800 pound 18 foot single axle trailer - - the trailer outweighed the car by
almost 1,400 pounds and definitely pushed the car around even with Reese weight
distributing hitch and friction type sway controls.  An accident where a
passing semi caused severe yaw resulting in a 180 degree spin was the last time
I towed a single axle trailer.

To me, what it boils down to is a combination of consumer (personal)
preference, competitive pressures, and concern about the potential for
regulatory intervention.  For many, like myself, it is a preference born of
unpleasant experiences with a particular trailer - - - not necessarily
supported entirely by facts and statistics.

I suspect that there really wasn't one particular reason for the switch from
single to tandem axles,  rather a series of circumstances that made the switch
advisable.  (IMHO)  To me, I have found the tandem axle trailer to be more
stable and forgiving of drive error than my single axle ever was.  In addition,
it is much easier to source tires of sufficient weight carrying ability for a
tandem axle setup than would be the case for a single axle trailer of similar
weight.  While many prefer the backing characteristics of a single axle, I have
found the reverse to be true - - my tandem axle responds much more predictably
than my single axle did when backing into a tight space.  The trailer seems to
be much more stable on the highway, but this is another personal preference
issue.  There are certain givens - - if the second axle was equipped with the
optional trailer brakes (the trailer brakes were optional on the second axle on
my '64 Overlander), you have an extra pair of brakes to assist in stopping the
trailer in all towing situations - - if one tire blows on a tandem axle the
trailer will likely be more controllable as there will still be one serviceable
tire on the same side.  The down side is that you have the extra set of brakes,
shocks, bearings, and tires to service on the tandem axle models.

Kevin Allen
WBCCI/VAC #6359
1964 Overlander International/1999 GMC K2500 Suburban