How Backing Up Towed Vehicles Works

Towing a vehicle can be stressful. Pulling the weight of another vehicle changes the way your own car, truck or SUV feels and behaves. You might even have to make some changes to your vehicle to tow another one safely. For the driver, perhaps the most stressful of all towing maneuvers is backing up a towed vehicle.

There are several issues you have to take into consideration when towing any vehicle. One of the most important is visibility. You may need to install larger side-view mirrors on your vehicle to improve your line of sight. Mirrors play a critical role whenever you have to back up -- you need to have a clear line of sight around both sides of the towed vehicle.

It's also important to make sure the vehicle that's doing the towing can handle the load. That includes reading the owner's manual to make sure you don't exceed towing weight limits. You should also make sure the trailer equipment is installed properly.

There are three major ways to tow a vehicle:

Four-wheels-down, toading or dinghy towing, is a towing method in which all four of the towed vehicle's wheels are on the ground. This method of towing is popular among recreational vehicle (RV) owners, who will often tow a vehicle behind their RV when traveling. This kind of towing requires a hitch and tow bar. Dinghy towing doesn't work well with some vehicles -- consult your owner's manual before attempting to toad your car.
Some vehicles work well with a tow dolly, which lifts the front two tires off the road. The towed vehicle's rear tires still make contact with the ground. A tow dolly cannot be used with most mid- or rear-mounted engine vehicles. Before using a tow dolly, you should learn the dolly's towing capacity. You should never attempt to back up a vehicle on a tow dolly -- while it's possible, it's not safe and can damage both vehicles. If you need to back up, the only safe option is to detach the two vehicles and back them up individually.
Four-wheels-up is the final towing option. With this option, you actually tow a trailer. The towed vehicle sits on top of the trailer, meaning none of its own wheels touch the ground. Tow trailers weigh more than tow dollies, but it's not as difficult to back up with a tow trailer as it is with a dolly.

We'll take a look at how to back up while towing a vehicle using either the four-wheels-up or four-wheels-down method. Because backing up with a tow dolly can be dangerous, we won't cover that option in this article. It's best to follow the advice of the experts with tow dollies -- try to avoid situations where you have to back up. If you do have to back up, do so with each vehicle individually.

Let's look at the physics involved with backing up a towed vehicle.

The Physics of Backing Up Towed Vehicles

Several factors make backing up a towed vehicle more complicated than just putting the car into reverse and going for it:

The towed vehicle adds more length to your overall setup.
The towed vehicle and towing apparatus adds more weight to the setup.
All of the extra weight is located behind the tow vehicle (unless something has gone very wrong).
The towing apparatus includes a pivot, which affects how the tow vehicle makes turns.
The two vehicles apply force to one another, which changes the way the tow vehicle can accelerate, brake and turn.

To tow a vehicle safely, it's good to have a basic understanding of physics. Here's a quick rundown on the physics of towing a vehicle:

Because the tow vehicle has to pull or push more weight than normal, it must deal with a different level of inertia. Inertia is the tendency for an object to resist a change in its state of motion. It's not a constant value -- objects with different masses have different values of inertia. An object with greater mass will resist changes to its state of motion more than an object with less mass.

To overcome inertia, the tow vehicle's engine must perform more work than it would for the vehicle on its own. The change in motion is called acceleration. Acceleration is a vector quantity, which means it has both a direction and a magnitude. With acceleration, that magnitude is a change in velocity.

In the case of backing up a towed vehicle, the direction of acceleration would be backward -- from the perspective of someone sitting in the driver's seat of the tow vehicle. To move in reverse safely, the driver must press down on the accelerator pedal carefully.

Once in motion, assuming both vehicles are on a level surface, the driver must continue to press the accelerator so that the engine will provide a constant force to the towed vehicle. That's because of friction. Friction is a force exerted by a surface as an object moves across it. In this case, friction applies a force opposite to the one applied by the driver. If the driver did not apply a constant force through the accelerator pedal, the two vehicles would eventually stop on their own.

When you're backing up a towed vehicle, you have to be careful not to move too quickly, because inertia also plays a factor when you apply the brakes. Remember, inertia refers to an object's resistance to changes in motion. If an object is moving, it will resist forces trying to stop it. When you're dealing with an object with a lot of mass -- two vehicles joined together, for example -- the inertia involved means more work is required to slow and stop the object's motion.

Next, we'll look at some techniques for backing up while towing a vehicle.

Techniques for Backing Up Towed Vehicles

Before you head out on the road while towing a vehicle, you should take some time to practice. Even simple maneuvers become more complicated and dangerous when you tow a vehicle. You have to use caution when making turns, braking, going up and down hills and backing up.

Try to find a large parking lot that isn't in use during part of the day -- a church or school parking lot could work. If it's possible, bring someone else along to act as a spotter. This will prevent you from having to rely entirely upon your mirrors.

When you are ready to practice backing up, place one hand at the base of your steering wheel, also known as the six o'clock position. From this position, the towed vehicle will turn in the same direction that you move your hand: move your hand to the right, turning the wheel counter-clockwise, and the towed vehicle moves to the right.

Remember to use small adjustments when backing up. The towed vehicle's movements will be much larger than the small adjustments you're making to the steering wheel. If you turn the wheel too far, the towed vehicle will make too sharp a turn.

Your spotter can help guide you. Always pay careful attention to your mirrors. Most importantly, take it easy. A slow and steady approach will help prevent accidents or damage to either vehicle.

It's much easier to back up a towed vehicle in a straight line than it is to turn while backing up. If it's at all possible, you should position your vehicle so that you can back up without turning. This will make the maneuver much less stressful on you and your vehicles. But if you can't back up in a straight line, it's better to use a gradual arc rather than a sharp turn. You'll have more control and visibility that way.

When you're done practicing and you're out in the real world, it's also important to take a good look at your environment before backing up a towed vehicle. Don't just look for problems at ground level. There may be low-hanging branches or street signs that you'll need to keep an eye on. That's why going slowly is a good idea -- it gives you more time to assess the conditions around you and make the appropriate adjustments.

To learn more about towing and related articles, hitch a ride to the links on the next page.

How Backing Up Towed Vehicles Works

The Physics of Backing Up Towed Vehicles

Techniques for Backing Up Towed Vehicles

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