Neglecting your tires will not only cause them to wear prematurely but could adversely affect the handling of your car. Three things every owner should do to prolong tire life are: maintain proper tire inflation, rotate the tires at least every other oil change (providing all the tires are the same size), and the subject of this article, regularly checking the vehicle's wheel alignment.
A wheel alignment is often called a front-end alignment, steering alignment, or steering balance. Simply stated, it involves adjusting the angles of the wheels so they are perpendicular to the ground and parallel to each other to ensure the vehicle tracks straight and true.
The theory behind wheel alignments requires balancing the steering angles with the physical forces being exerted on the vehicle. The objective is to achieve a balanced weight distribution on the wheels and proper tire contact with the road surface while the vehicle is in motion. So by regularly checking and measuring the angles of critical suspension and steering components and comparing these data against a set of desired specifications, a skilled technician is able to determine if the vehicle is out-of-alignment.
An out-of-alignment condition can be caused by spring sag, suspension wear as the vehicle ages, or after a vehicle encounters a major road hazard or curb. The end result is the same: The tires will wear prematurely and handling of the car will suffer. In this regard, there are several different types of wheel alignments. They are front-end, thrust angle, and four-wheel alignments.
During a front-end alignment, only the front axle's angles are measured and adjusted. Front-end alignments are fine for some vehicles featuring a solid rear axle, but confirming that the front tires are positioned directly in front of the rear tires is also important. On a solid rear axle vehicle, this requires a thrust angle alignment that allows the technician to confirm that all four wheels are "square" with each other. With four-wheel independent suspensions or front-wheel drive vehicles with adjustable rear suspensions, the appropriate alignment is a four-wheel alignment.
This procedure squares the vehicle like a thrust angle alignment, and also includes measuring and adjusting the rear axle angles as well as the front.
Here are some basic terms used in wheel alignments:
Camber is the angle of the wheel when viewed from the front of the vehicle. If the top of the wheel is leaning out from the center of the car, then the camber is said to be positive. If it's leaning in, then the camber is negative. If the camber is out of adjustment, it will cause tire wear on one side of the tire's tread. But different driving styles can also influence the desired camber angle. An aggressive driver, for instance, may ask for more negative camber to increase cornering grip. However, if the same specifications are used on a conservative driver's car with lower cornering speeds, it would actually cause the inside edges of the tires to wear faster than the outside edges.
Caster is the angle of the steering pivot when viewed from the side of the vehicle. Caster angle settings allow the manufacturer to balance steering effort, high-speed stability, and front end cornering effectiveness. If the top of the pivot is leaning toward the rear of the car, then the caster is positive. If it is leaning toward the front, it is negative. If the caster is out of adjustment, it can cause problems in straight-line tracking. If the caster is different from side to side, the vehicle will pull to the side with the less positive caster. Caster has little affect on tire wear however.
The toe measurement is the difference in the distance between the front of the tires and the back of the tires when viewed from directly above. Toe-in means that the fronts of the tires are closer to each other than the rears. Toe-out is just the opposite. Toe can also be used to alter a vehicle's handling traits. Increased toe-in will typically result in reduced oversteer, help steady the car and enhance high-speed stability. Increased toe-out will typically result in reduced understeer, helping free up the car, especially during initial turn-in while entering a corner.
The thrust angle compares the direction that the rear wheels are facing in relation to the centerline of the vehicle. It also confirms if the rear axle is parallel to its front axle and that the wheelbase on both sides of the vehicle is the same. If the thrust angle is not zero, then the vehicle will "dog track" and the steering wheel will not be centered. This is normally done during a 4-wheel alignment as long as the rear toe is adjustable. If the rear is not adjustable, then the front toe must be set to compensate for the thrust angle, allowing the steering to be centered.
A wheel alignment is an important suspension-tuning tool and will usually save you as much in tire wear as it costs - it should be considered part of your routine, preventative maintenance. As it relates to the extremely poor condition of the roadways in and around the Mildmay area, John actually recommends having your car(s) checked at least twice a year (most reputable shops do not charge anything just to check if the wheels on your car are properly aligned). An alignment should also be done whenever new tires or suspension components are installed, or any time an unusual tire wear pattern develops. As it relates to this last point, an experienced technician using the latest wheel alignment equipment from Hunter Engineering, for example, is invaluable.