Towing Safety
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Towing Safety

Thinking about buying a trailer or renting one? If you’re new to towing, there are a few things you should know to make sure you and your cargo are safe.

Weight and Size

You probably know that the trailer should weigh less than the Gross Trailer Weight (GTW) rating of the vehicle, but it can also affect the vehicle’s cargo capacity: with the tongue putting hundreds of pounds on the rear end, it’s easy to go over the Gross Vehicle Weight Rating (GVWR,) which can cause problems with handling and braking.

If the trailer’s wider than your vehicle, you’ll need extended side view mirrors to see behind you. Some trucks come with extendable mirrors, while clip-on mirrors can be added to other mirrors.

When loading a trailer, the weight needs to be balanced left to right to keep it tracking straight.


Hitches are divided into classes designed around Gross Trailer Weight (GTW):

Class 1 — 2,000 pounds
Class 2 — 3,500 pounds
Class 3 — 5,000 pounds
Class 4 — 7,500 pounds
Class 5 — 10,000 pounds

Getting the highest class hitch your vehicle can support will make towing safer, even if you’re using a light trailer. The hitch ball is usually 1 7/8 inches for Class 1 and 2 trailers, while everything else uses 2-inch balls.

Tongue Weight

The tongue weight of the trailer should be 10-12% of the trailer’s total weight. If it’s too low, the trailer will sway, and if it’s too high, it can lift the vehicle’s front end, making it hard to steer. Measuring the tongue weight on small trailers is easy: just put it on a bathroom scale. If you have a larger trailer, you can construct a lever using a wood board, supporting one end with the scale and the other with a wood block. The distance between the block, tongue and scale determine how much you need to multiply the results: if there’s an equal distance between all three, the scale will show half the actual weight.


There are two kinds of brake systems used on trailers:

Surge brakes have a master cylinder attached to the tongue. When the vehicle slows down, the tongue pushes on the cylinder, operating the brakes. There is no direct connection between the trailer brakes and the tow vehicle.

Electronically controlled brakes link electric trailer brakes to the tow vehicle’s brake pedal and a manual lever on the control box. These brakes connect to the vehicle using the wiring included in a 7-way connector. Always check the battery voltage before using the trailer: if it’s dead, the brakes won’t work.

Wisconsin requires brakes on trailers over 3,000 lbs., while some states require brakes on trailers weighing as little as 1,500 lbs.


Federal law requires full lighting with turn signals for trailers used on highways, while Wisconsin requires at least one red light on the rear and a directional lamp on each corner of the trailer. Some small equipment trailers don’t come with lights from the factory, so they need to be added to make the trailer legal to use in this state.

Hooking Up the Trailer

Before you hook up the trailer, make sure all the tires are in good shape and aired up.

Start by lowering the hitch onto the ball and latching it. Move the tongue around to make sure the connection is tight.

Next, attach the safety chains to the holes next to the hitch. These should cross under the hitch and be loose enough that the trailer can make sharp turns, but not so loose that they’ll drag on the ground.

Most trailers connect to the vehicle electrical system by a 7-way or Flat-4 connector. Once connected, check the lights and brakes to make sure they’re working properly.


Driving with a trailer is a lot like driving on snow and ice: movements should be gentle when turning, braking or accelerating to maintain traction and stability. Sudden movements can induce sway and in severe cases cause jackknifing. Some vehicles have a tow mode, while most vehicle manufacturers recommend turning off overdrive (O/D) to get more torque to the wheels.

If the trailer starts swaying, reduce your speed. Electronic brakes can be manually applied using the control lever to help bring it back in line. If the trailer continues to sway, pull over and check the contents of the trailer. When items shift around, it can upset the weight balance on the tongue or between the left and right sides of the trailer.

Accidents Can Happen to the Best Prepared Drivers

Using a trailer puts you at a higher risk of having an accident no matter how safe you drive. If that happens, visit Merton Auto Body for the experts in collision repair. We have a staff of ASE-certified technicians and we’re I-CAR Gold Class certified, so we have the training and techniques to get your car or truck looking and driving as good as new. Worried about lengthy repairs? We have an auto body appraising center to get work approved by your insurance company, so you’ll have your vehicle back in no time. Stop by our website to learn more at or visit our convenient Sussex, WI location. We proudly service the Waukesha County and surrounding Lake Country areas, including Oconomowoc, Delafield, Pewaukee, and Hartland.



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