How Steering Works

This diagram shows you the...        read full caption This diagram shows you the basic components in a steering system and how they’re linked. The specific parts of your truck’s setup may differ, depending on its make, model, and front suspension design (solid axle or IFS), but the theory behind how it works still applies.

If you’re planning to go up in tire size and/or lift your suspension, don’t forget to put steering components on your wish list. They’re not as sexy as tall springs, adjustable shocks, or a biting tread pattern, but they play a crucial role in your truck’s performance. If you lift your truck without modifying its steering, you may encounter some serious problems when it comes time to round that first corner. And you can guess where those kinds of problems will lead, right? Off the trail and into a ditch, most likely.

Most suspension companies recognize that lifts and steering mods go hand-in-hand. So they make steering components, designed to rectify the changes in steering geometry that come with pushing the tires away from the chassis, an integral part of their complete lift systems. But not everyone can (or wants to) use these off-the-shelf systems. And there are others who need even more steering beef because of huge tires or extreme ’wheeling conditions. Or both. For those folks, and for those of you who want to know more about pitman arms, drag links, and other steering components, we’ve compiled this guide to steering system upgrades.

In this first part of our Steering Special, we’ll revisit the basics of how steering works. In the stories that follow, we’ll show you what it takes to make a 4x4’s steering system work properly after a suspension lift, followed by a look at some of the pieces used to beef up steering components.

HOW IT STEERS

A truck’s steering system is designed to turn the rotational action of steering wheel movement into the linear action of pushing the tires in the desired direction of travel. That process goes like this (sung to the tune of, “the knee bone’s connected to the thigh bone...”): The steering wheel is connected to the rest of the truck’s steering componentry via the steering shaft. That shaft feeds into the steering box (in a typical recirculating-ball steering system), and the box’s output shaft is connected to a pitman arm. On the other end of the pitman arm is a drag link, connected to a series of rods, which themselves are connected to steering arms on the knuckles at each wheel spindle.

In independent front suspension (IFS) applications, a couple of other components are typically added to the mix. The pitman arm is connected to a center link, which spans the distance between the axle’s halfshafts. On the passenger’s side, an idler arm is also connected to the center link to basically support the link and mimic the motion of the pitman arm. The tie rods then run from the center link to the steering arms.

So, turning the steering wheel rotates the steering shaft, which turns a worm gear in the steering box. The worm gear is one of several gears in the box that translates steering shaft rotation into the back-and-forth movement of the pitman arm, which pushes on the link-rod-steering arm assembly to point the tires in the direction of travel. Make sense?

The term “suspension geometry” refers, in part, to the proper alignment of the steering system’s various arms, links, and rods. All of these parts have to line up at a certain set of angles, and move through a specific range of motion without losing their angular relationship to each other, to work properly.

A second component in the suspension geometry equation is wheel alignment. Alignment is the proper orientation of the wheel and tire to the suspension system and to the road surface, and it’s measured (and adjusted) in several ways. (See the sidebar Alignment 101 for a more detailed description.) When a truck’s tires are correctly aligned, it will track straight down the road without pulling to one side or the other, the tires will wear uniformly, and it will be able to resist an effect called bumpsteer, in which the vehicle tends to wander or dart around when it encounters a road irregularity like a pothole.

HOW A 4x4 IS DIFFERENT

All that basic steering theory applies to any vehicle, from subcompact cars to heavy-duty 4x4 pickups. But the way a typical 4x4 is used and—more importantly—modified can negatively affect a factory-stock steering system, which in turn can degrade steering performance.

A suspension lift can wreak havoc on the steering system’s geometry. Most tie rods and track rods are designed to work best when they’re following the axle’s range of movement, or are somewhat parallel to the ground. Lifting the suspension pushes the spindles farther away from the chassis than they were designed to be, which can put the tie rods and drag links at odd angles. The rods and links may not be long enough to provide their full range of motion, or they may bind (and possibly break) at the point where they’re connected to the tie rods and steering arms. Either situation is a problem that could result in a loss of stability and steering effectiveness, or even the total loss of steering ability.

Lifting the suspension and mounting larger-than-stock tires will also affect the wheel alignment. If the alignment specifications aren’t changed after the modifications are completed, you could lose directional stability and suffer uneven tire wear. And who wants that after throwing down all those big bills on new rubber?

It’s difficult to come up with a hard-and-fast rule about how much you can lift a 4x4 before negatively affecting the steering system, since the suspension and steering setups vary so much from vehicle to vehicle. But figure that a 4-inch-or-greater lift is going to require steering mods. At 2 to 3 inches you should check with your suspension system manufacturer or local 4x4 shop to see what may be needed.