Another important point that goes along with the coupler is the hitch itself. It should be of the receiver type with the proper drop to match the trailer tongue height so that the trailer is level. The receiver should be mounted to the frame-not the bumper-as high as possible. With the hitch removed, little ground clearance is lost. Note again that the receiver should be attached directly to the vehicle's frame. Sure, that heavy-duty bumper may supposedly support 500 pounds of tongue weight, but that's for highway use. Under heavy four-wheeling loads, that tongue weight, because of leverage factors, can get multiplied several times over. (We speak from experience-stock bumper brackets just don't do it.) A lot of custom and aftermarket receivers mount to both the vehicle's frame and to the bumper. These are great because both hitch and bumper benefit.
Trailer balls: use a one-piece ball that's rated for the total weight being towed. Trailer balls come in 17/8-, 2-, 25/16-, and 3-inch sizes. Who originally decided on these sizes, we'll never know. The most common is the 2-inch size. Forget about using two-piece balls. The two-piece ball is made of a cast material with a steel center bolt, and it doesn't have anything near the strength of a one-piece machined ball. The two-piece units are actually illegal in some states.
Not only does the diameter of the ball determine its capacity, but shank length, shank diameter, and ball rise all need to be taken into account, as well as whether the ball is cold-formed machined or hot-forged. The longer the shank (threaded portion) or taller the rise (the distance from the flange to the top of the ball), the less capacity available per given diameter. All 17/8-inch balls are rated at 2,000 pounds and generally have a 3/4-inch-diameter shank about 11/2 inches long, or are one inch in diameter with a 2-inch-long shank. The common 2-inch ball is rated between 3,500 and 5,000 pounds, again depending on the aforementioned factors. Shank diameters are usually 3/4 or one inch. The 25/16-inch balls use a 1-, 11/4-, or 13/8-inch-diameter shank and are rated between 5,000 and 30,000 pounds. The 3-inch ball used with "gooseneck" trailers has a 2-inch shank and a 20,000 pound rating.
Because of the various factors involved, how do you know the capacity of the ball? The manufacturer stamps the ball's maximum capacity right on top of the ball head. It might not be a bad time to check your ball's capacity. Most likely, you'll find that you're under capacity.
While you're at it, check the capacity of your coupler, which is stamped into the housing. It doesn't make a lot of sense to use a 5,000-pound-rated ball that's hooked to a 3,500-pound coupler. For example, say you trailer your Jeep. It only weighs 3,000 pounds, but the trailer weighs another 1,000 pounds, not to mention any tools, chains and binders, extra gas, and camping gear that may be along for the ride. Having a coupler and ball in the 25/16-inch range now becomes a necessity. What about the safety chain? Is it up to the combined weight in case of a hitch failure?
Next month, we'll tell you a bit more about trailers and talk about brakes and load balance.