Some 4x4 owners never modify the stock suspension on their vehicles, but most do. The primary goal of a suspension modification is to raise the body and frame of the vehicle to create additional ground clearance. This also provides room for larger tires and increases suspension travel, which refers to the amount of vertical wheel movement allowed by the suspension.
Several manufacturers make lift kits, or lift systems, specifically for this purpose. Before you invest in a lift kit, think about your off-road driving habits. High-speed desert running requires a much different suspension modification than rock crawling. And don't forget to think about the on-road driving you'll have to do. If you have a dedicated off-road vehicle -- one that will be towed to and from the trail -- you might consider an extreme kit. Most people aren't that lucky, so they choose a kit that provides good performance on both street and trail.
There are two basic types of lift kits. To understand the difference, it helps to visualize the foundation of an off-road vehicle. Most trucks and SUVs feature body-over-frame construction. In this design, a steel frame acts as the foundation onto which the body and all major parts are attached. Now let's tackle suspension lift kits. These kits raise a vehicle by suspending the frame, body, engine and power train above the wheels. In other words, the distance between the axles and the chassis increases. Such a kit typically costs more and requires more installation expertise to handle any braking, steering and axle modifications that must be made to the vehicle.
Body lift kits, the second type, work a little differently. They use a system of blocks, or spacers, to raise the body above the frame. In other words, only the distance between the body and the frame increases, which means the geometry of the power train and the steering is not affected. You still enjoy more clearance for your tires without having to modify any of the core suspension components. As a result, body lift kits cost less and require less installation expertise.
Lift kits make your vehicle more functional, but they don't necessarily make it a smooth ride. In the next section, we'll discuss the equipment you'll need for cushioning that bumpy ride.