JDH wrote:
Steve Hopper wrote:

For anyone out there who knows about trailers:


Trailer stability is a complex subject, and the subject of many
old-wives tales and outright misinformation. There are a number of SAE
papers on the subject if you're up to the math. There is also a pair
of excellent books about trailers by M J. Smith (I'm not certain of
those initials) that every trailer owner should buy and read. She does
a good job of translating the technical papers into English.
Basically, every tag trailer/tow vehicle combination has a speed at
which it will become unstable. Once this speed is reached, you become
a passenger. Fortunately, things start to feel a little squeamish
slightly before that. You want the stability limit to be comfortably
higher than your planned maximum. The two most critical factors a
distance from the tow vehicle's rear axle to the ball (smaller is
better) and the distance from the ball to the trailer axle (bigger is
better). Once the vehicles are designed, the only variables you have
are tongue weight and tire inflation. More tongue weight increases
stability through an indirect mechanism, but it's a poor substitute for
a good design. It is possible to have a trailer that is unstable even
with large tongue weights (I had one). Home built trailers seem
particularly prone to this. In such a case, the only choices are to
fabricate a tongue extension or cut it up for scrap (I did the latter),
although a really heavy tongue weight and a load-equalizing hitch might
get you by. Dual axles and their suspension (or lack of it) introduce
additional compexities as noted in this thread. I don't envy you your
choices here, but if your trailer is tossing around a long-wheelbase
pickup at 40 MPH, it's a bad one. Get rid of it before it kills you.
John


Thank you John for this valuable information. The trailer in question
is a home-built. I bought it from the estate of an old farmer and it
had probably never been used except behind a tractor. I have a feeling
that I can improve the towability of this trailer by lowering the
level at which the trailer is connected to my hitch; it think it's
too high. Again, thank you and everyone for their thoughts and
suggestions. sdh.