Leveling The LoadOnce you've chosen the proper hitch, you still must load the towing vehicle and trailer properly. When the trailer is fully loaded, does the trailer or hitch drag over bumps? Does your vehicle suffer from sway, road wander and fishtailing at speed? Does its rear end sag? When you're towing at night, do oncoming drivers flash their bright lights at you as you approach? If you answered yes to any of these questions, you might be a prime candidate for a load leveling device.

Several products are designed to help vehicles with leaf springs in the rear (which is most vehicles on the road) handle the extra load. The first product, aptly enough, is called helper springs. Another choice is a set of air springs.

Helper springs attach to your stock leaf springs and usually come into play only when you're hauling a heavy load or towing. They essentially increase the spring rate-but under normal driving conditions, they won't affect your vehicle's ride quality. Helper springs also can come in handy if you've installed heavy accessories on the back of a truck, such as a winch, a serious rear bumper or even a truck cap.

Air assist systems work in a similar manner, but a bit more elegantly. These packages include air springs that are added to your existing suspension. When you aren't towing or hauling a load, you leave the pressure in these springs nice and low, so you don't even know that they're there. Then, when you need to level your vehicle, you simply pump up the springs. Plus, because you use air to fill them, air springs are infinitely adjustable, which means that you can precisely tune your rear end's ride height until it's level with the front. Another plus: air assist packages are available for vehicles that have coil springs in the rear, instead of leaf springs.

To increase your vehicle's stability when it's towing, you may want to make a few additional suspension upgrades. For example, anti-sway bars (also called sway bars or stabilizer bars) are designed to reduce body roll (when your vehicle leans to one side during a turn). Most SUVs come with anti-sway bars front and rear, but they're quite small in diameter, and many pickups only come with a front bar. A swap to larger bars for the front and rear will dramatically improve a vehicle's cornering ability.

For more control when you're going straight, a good set of shocks can make a world of difference. High-performance shocks will stabilize your vehicle, so it doesn't bounce as much after you hit a bump or pothole. They will also smooth out the feel of potholes, railroad tracks and other road irregularities, improving your vehicle's ride quality. Plus, good shocks also can help reduce body roll.

Several companies offer shocks that are adjustable, too. This means that you can set the shocks for a comfortable ride when you don't have a heavy load. Then, when it's time to tow or haul, you simply change to a stiffer setting so you avoid getting bounced around inside the vehicle-and to keep the rear end from sagging.

"All vehicles are equipped with suspension springs, which support the weight of the vehicle," according to Mike Morgan, national sales manager for the Air Lift Co., which manufactures air helper springs and air ride systems. "Factory springs provide a comfortable ride and good handling, but only until they're placed under the strain of a heavy load," he explains. "This leads to suspension sag, bottoming out and poor handling characteristics. When a vehicle rides at an attitude other than level, its drivability degenerates." While some of these problems can be mere annoyances, others are dangerous.