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Gear Test: SenZBar digital draw bar

We’ve all seen tow vehicles with their rear bumpers dragging near the ground and the trailer swaying all over the road, or the less obvious but equally dangerous vehicle that is higher in the rear than normal with a trailer attached.

We’ve all seen tow vehicles with their rear bumpers dragging near the ground and the trailer swaying all over the road, or the less obvious but equally dangerous vehicle that is higher in the rear than normal with a trailer attached. One of the main reasons for these unsafe practices is lack of knowledge regarding the trailer’s tongue weight and how to adjust it.


Tongue weight is the portion of the trailer’s overall weight that is pressing down on your tow vehicle’s trailer hitch or tow ball. Industry experts say boat trailers should have a tongue weight between 5 and 7 percent of the trailer’s GTWR (gross trailer weight rating, or the combined weight of the trailer, boat and accessories). Too much tongue weight presses the rear of the tow vehicle down, lifting the front wheels, which creates a loss of steering control and limits front-wheel braking while compromising overall traction. It also can damage the tow vehicle’s suspension and drive train.

Too little tongue weight can be worse, lifting the rear of the vehicle, reducing rear-wheel traction and causing instability that can result in trailer sway or jackknifing — especially when braking. And forward weight transfer further reduces rear traction. With the trend toward smaller and lighter tow vehicles, correct tongue weight is more critical than ever.

To correctly determine what your trailer tongue weight should be, you need the GTWR, which you can obtain by towing your boat to a public scale, such as those found at recycling centers. You can estimate GTWR by adding the manufacturer data and the weight of your regular cargo, such as fuel and accessories.

Once you have determined GTWR, there is an easy way to calculate tongue weight. SenZBar is a digital draw bar with a remote display that shows the tongue weight quicker than you can than check tire pressure. The draw bar is Class 3-rated and can safely tow a 6,000-pound (GTWR) trailer with up to a 600-pound tongue weight, according to manufacturer Reese Hitches. The advertised measurement capacity of the SenZBar is 1,000 pounds, with a tolerance of plus or minus 5 percent, although independent lab tests show its accuracy remains constant far in excess of that number.

The SenZBar accepts Class 3 hitch balls with a 1-inch shank, and provides the most common ball mount drop of 2 inches and a rise of 1 inch when inverted. It is calibrated for use in standard 2-inch-square U.S. receivers, where the distance from the center of the receiving pin hole to the edge of the receiver is 2.5 inches. The exterior of the bar is powder-coated bright yellow for durability.

The remote display unit measures about 3.5 by 7 inches and is powered by a 9-volt battery. It has a 2-foot multipin interconnect cable that attaches to the draw bar through a 3/8-inch hole in the left side of the draw bar shank. A hinged foot allows the display to stand independently, and the digits on the LCD readout are a half-inch tall. Operation is simple: Plug the display into the draw bar, turn the unit on, couple the trailer and read the tongue weight.

I used my 21-foot twin outboard Boston Whaler and Owens trailer to test the SenZBar, as I had already established the GTWR (3,850 pounds) and tongue weight the old fashioned way. The SenZBar indicated a tongue weight of 375 pounds, almost 10 percent of the GTWR.

I placed 180 pounds in the boat abaft the axles, which reduced the tongue weight to 345 pounds; placing it amidships increased the tongue weight to 415 pounds. As you can see, it doesn’t take much to significantly change tongue weight. Most boat trailers provide enough flexibility for you to alter the tongue weight considerably just by sliding the boat forward or aft a foot or so, which should be done when the boat is loaded onto the trailer. Once the initial setup is done, fine-tuning can easily be accomplished by moving cargo.

The SenZBar readings were consistent each time I coupled the trailer, and the unit appears durable enough for full-time use. The manufacturer, however, does caution against submerging the draw bar. The display unit should be treated carefully, as with any precision instrument, and doesn’t appear to be protected from the environment aside from its plastic housing. The manufacturer includes a small magnetic cap to cover the connection port in the draw bar, which doesn’t fit very well and, in my opinion, is inadequate. Water, sand and road debris will find its way into the connection port. A properly fitted rubber plug or threaded plastic cover would be better suited for the task — and in line with the overall quality of the SenZBar.

I’m not suggesting that you check the tongue weight each time you couple your trailer, but it is a good idea to establish a baseline and understand how it is affected with various loads and their positions. SenZBar makes this task almost effortless.

The product appears to be well-constructed and certainly fills a need for anyone that tows a boat. The SenZBar retails for $149.99, which I find reasonable for the safety and peace of mind it affords. SenZBar can be ordered directly from the manufacturer at .