Tow The Line
What You Need To Know To Safely Handle A Trailer
By Mike Berger
Publication: Handy (Handyman Club of America Magazine)
Issue: August 2006
Pg. 42, 44 – 47
You’ve decided to tackle that next home improvement project – good for you! You’ve done your homework and drawn up your materials list, and you’re ready to go shopping. But then you realize it’s going to be awfully hard to fit all of that lumber into your vehicle. Rather than pay a delivery charge (and be tied to a delivery schedule), you decide to haul everything yourself on a trailer.
Before you rush out to rent a flatbed, however, you need to understand the basics of towing. If terms such as “tongue weight” and “trailer weight allowance” seem like some type of arcane mathematics, let us demystify towing for you. It may surprise you how easy it is to stay safe on the road while towing a load.
Basic Towing Gear
To avoid damaging your vehicle and trailer – not to mention endangering others’ lives – it’s essential that you understand the following towing gear:
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Hitches – Towing hitches are differentiated by the amount of weight they can pull (see table, p. 49) and are divided into three categories: weight-carrying hitches, weight-distributing hitches and fifth-wheel or gooseneck hitches (which, because of their specialized nature, are beyond the scope of this article).
Weight-carrying hitches are designed to carry all of the trailer’s tongue weight (see “Understanding Weight,” opposite) and come in two basic styles: drawbar and receiver. A drawbar hitch is a one-piece welded unit with a fixed ball mount that permanently protrudes from the rear of the vehicle. A receiver hitch allows the ball mount to be removed so that nothing projects beyond the vehicle’s bumper (photo, above left).
A weight-distributing hitch differs from the weight-carrying variety in that it distributes the towing load among all of the axles of the tow vehicle – not just the rear axle – and helps to improve vehicle stability while towing. -
Hitch balls and mounts – Like trailer hitches, hitch balls are assigned a maximum tongue weight (TW) and gross trailer weight (GTW) rating. Balls come in a variety of sizes – 1-7/8 and 2-in.-dia. balls are the most common – and you should chose the size that matches the size of the ball socket of the trailer’s coupler.
For extremely light-duty towing, the hitch ball screws directly into the rear bumper of the tow vehicle. But for receiver-style hitches, the hitch ball attaches to a ball mount that slides into the receiver hitch and is secured with a locking pin. -
Chains – Safety chains prevent the trailer from coming loose from the tow vehicle if the hitch fails. Chains should be long enough to allow for tight turns and be crossed (right to left and left to right) when attached to the tow vehicle to aid in controlling the trailer.
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Braking systems – Large trailers and those designed to carry heavy loads often feature brakes that work with the tow vehicle’s braking system. Electronically controlled brakes operate via a control box that is usually installed within the driver’s reach and can be adjusted to match the trailer’s load. Surge brakes are independent hydraulic brakes activated by a master cylinder mounted on the trailer. These systems do not require adjustment for variations in the trailer’s load.
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Lighting connections – To be street-legal, a trailer must have operating taillights, brake lights and turn signals. The lights connect to the tow vehicle via a multiple-pin plug and work in conjunction with the vehicle’s lighting system. (When you step on the brake pedal, you activate the trailer’s brake lights.) A variety of plug configurations and adaptors are available to match the trailer’s wiring plug to that of the tow vehicle.
Driving With A Trailer
Successfully attaching a trailer to a tow vehicle is only half of the equation. Understanding how the trailer handles on the road and being able to drive appropriately can mean the difference between safe operation and an accident waiting to happen.
After hooking the trailer to your vehicle, walk around and inspect all of the connections and trailer components. Check that the lights and indicators function properly, that the tongue is securely mounted within the receiver and that the ball is firmly bolted to the tongue. Make sure that the trailer’s coupler is securely locked, that the chains are crossed and firmly latched to the vehicle and that the trailer’s emergency brake cable is connected to the tow vehicle.
Always use the driving gear that the vehicle’s manufacturer recommends for towing. Avoid sudden stops and starts that can cause skidding or jackknifing, and drive at a moderate speed, as the trailer is more likely to sway at higher speeds. If the trailer begins to sway, slow down by removing your food from the accelerator rather than by braking.
Hills can present special problems to vehicles with trailers in tow. For downgrades, shift to a lower gear to aid in braking, and apply brakes at intervals to prevent them from overheating. When climbing, shift to a lower gear (as recommended by the tow vehicle’s manufacturer) to increase power, and keep an eye on the engine temperature, as the added strain may tax the cooling system and cause the vehicle’s engine to overheat.
Remember that the added length of a trailer in tow greatly affects overall turning ability. Because trailers have a tighter turning radius than that of the tow vehicle, you must make turns wider than normal. Be particularly careful in right-hand turns, as the trailer’s right corner or wheel may catch on an obstruction such as a signpost if you do not allow enough clearance.
Backing up a trailer takes practice, but it can become second nature. Start by placing one hand at the bottom of the steering wheel (photo, opposite). If you want the back of the trailer to go to the left, slowly move your hand to the left as you back up. If the trailer needs to turn to the right, simply move your hand to the right as you back up. The trailer will always turn in the direction in which you move your steering hand.
By understanding your towing equipment, knowing how your trailer responds and practicing safe driving, you can help to ensure that your load will arrive safely – and everyone else on the road will benefit from your efforts.
Understanding Weight
When you tow, be aware of five weight ratings:
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Tongue Weight (TW) is the downward force exerted on the hitch ball by the trailer coupler. In most cases, it is about 10 percent to 15 percent of the trailer’s gross weight. You can measure TW of up to 300 pounds by resting the trailer coupler on a household scale positioned so that it sits at normal towing height (such as atop a crate, as shown here).
For heavier tongue weights, place a household scale and a brick that’s as thick as the scale 3 ft. apart. Set a length of pipe on each and rest a length of 2x4 across the pipes. Reset the scale to correct for the weight of the beam and pipe; then block the trailer wheels and rest the trailer jack on the beam. Position the trailer jack so that it rests 1 ft. from the brick and 2 ft. from the scale. Multiply the scale’s reading by 3 to figure the trailers TW (photo, right). -
Gross vehicle weight rating (GVWR) represents the total allowable weight that the tow vehicle and the trailer are individually designed to safely carry.
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Gross axle weight rating (GAWR) is the maximum allowable weight that each axle – both for the tow vehicle and for the trailer – can support. In some cases it’s possible to be within the GVWR but still dangerously exceed the GAWR. For example, a small truck with a fully loaded cargo bed and a fully loaded trailer in tow could easily exceed the rear truck axle GAWR but still be within the overall GVWR.
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Trailer weight allowance (TWA) is the maximum weight the vehicle can safely pull. The TWA rating varies greatly and is directly affected by size of the engine, the type of transmission and the rear axle ratio, all of which can be found in the vehicle’s owner’s manual.
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Gross combined weight rating (GCWR) represents the combined weight of a fully loaded tow vehicle (fuel, occupants and cargo) and the total weight of the load in tow (trailer, cargo, etc.). Recommendations for maximum GCWR can also be found in the vehicle’s owner’s manual, but if you’re in doubt about the weight of the trailer and its cargo, have the trailer weighed at a local scale and obtain estimates of the cargo’s weight before loading it. - MB
Special thanks to SnowBear Limited for providing the trailer shown in this story.
SOURCES ONLINE - For online information, go to www.HandymanClub.com and click on SOURCES ONLINE.