How to Correct an Off-Center Steering Wheelby Richard Rowe
Depending on your perspective, an off-center steering wheel can be a truly infuriating experience, all the more so when the car doesn't pull to either direction. There's something about this condition that just seems to baffle the human mind; how can the car be going straight when the wheel is turned? But the reason for a steering wheel turn, and the subsequent fix, is actually pretty simple once you understand what went wrong.
Your steering wheel connects to a steering column. At the end of that column is a gear called a pinion, and that pinion meshes onto matching teeth on top of a flat bar called a rack. When you turn the pinion, it pushes the rack to the left or the right. The ends of the rack connect to tie rods, which in turn connect to arms extending backward from the wheel hubs. On the tie rods you'll find a threaded collar; turning it makes the tie rod longer or shorter, angling the wheel inward or outward. Of course, this describes only a rack-and-pinion system, but most steering systems are functionally identical where the steering linkage is concerned.
Rear Toe and Steering
Most cars also have a second bar running from side-to-side in the rear, and those that don't typically have some provision to turn the axle one direction or the other. While it may seem a bit strange, the rear axle and its tie rods are just as responsible for steering your car as the front. The difference is that the rear axle only turns the rear of the car. If your rear alignment settings -- via the tie rods or axle alignment -- are off, you'll have to turn the wheel in the same direction as the rear tires to keep the car pointed down the road. This alone will cause your steering wheel off-center, because the car is actually going down the road slightly sideways.
An off-center steering wheel is, paradoxically, a pretty common complaint following a front-wheel alignment. During an alignment, the technician will adjust your front tie rods to whatever degree necessary to remove any pull on the steering wheel. In the course of doing so, he'll end up changing the position of the wheels relative to the steering column just to keep them pointed in the same direction as the rear tires. While this does eliminate that sideways pull, it'll also permanently cock your car sideways. This "off-tracking" or "dog-tracking" is dangerous because it changes your car's low and high-speed handling characteristics, and it'll kill your fuel economy by exposing the broad side of your car to the wind.
Dialing Out the Turn
Since this is essentially a problem with rear wheel angle, you need to adjust that first. The simplest way is to take your car to an alignment shop and have them perform a four-wheel alignment. If you're doing it yourself -- which you shouldn't unless you've got the right equipment -- then you need to get the rear wheels pointed perfectly straight first. Then, you'll need to start the engine, turn the wheel a couple of times to relieve pressure from the power steering system. Shut the car down with the wheel locked in a straight-ahead, 12-o'clock position. Finally, adjust the front tie rods to get the wheels straight. At this point, the problem is essentially fixed and your car is once again pointed straight, but you're not quite done yet.
Setting the Toe
While it might sound odd, most cars aren't going down the road with all four wheels pointed straight forward. Many have a certain degree of front or rear "toe." Toe-in means the front of the wheels point inward, or sort of cross-eyed. Toe-out means they point slightly outward. Different manufacturers and drivers prefer different degrees of toe-in or -out for a given car. Toe-in makes that axle more stable on the highway and under braking by causing the wheels to constantly try to turn toward each other. Toe-out causes that axle to change direction more quickly at the expense of stability. A zero-toe setting does nothing for directional stability either way, but is the hypothetical optimum for fuel economy. Setting toe is vital for your car's performance and safety, and it's somewhat difficult to measure without the right equipment. So, unless you really know what you're doing, these sorts of alignment settings are best left to professionals.
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