Trailer Checkup
A trailer's inherent stability is part of its design, based on the amount of weight in front of the axles vs. the amount of weight behind. The difference between these two weight masses is the amount of weight on the trailers hitch, which is called the hitch weight or tongue wight.
Trailers with insufficient hitch weight have two deficiencies: The percentage of weight (mass) behind the axle(s) is too high, so when set in motion it acts as a pendulum; and the distance between the hitch ball and the trailer axles is insufficient.
Simply stated, trailers with a high proportion of hitch weight to gross weight usually have more of their length ahead of the axles, and they handle better. The generally accepted industry standard is that hitch weight should be approximately 10 percent of gross weight. In fact, that is a bare minimum, and some trailers with 10 percent hitch weight do not handle well. Hitch weights of 12 percent or higher (up to the weight limits of the hitch and vehicle beings used) assure proper handling.
In marginal situations, the owner's ability to handle and unstable trailer will depend on the inherent stability of the tow vehicle, which is yet another variable. A truck or van with a long wheelbase, a relatively short rear overhang and stiff springs often will at least partially make up for a trailer's lack of inherent stability, whereas if the trailer is towed by a softly sprung vehicle with a long overhang, the trailer's shortcomings will be more obvious.