One of the most important and yet neglected factors influencing the handling, and the fuel efficiency, of any car or truck is the wheel alignment. Your vehicle's ability to go, stop and change direction is affected by the direction each of the wheels is pointing, and, whether you drive a compact car or full-size SUV or pickup, the directional control you get where the rubber meets the road is important for safety.
At any given moment only a small patch of rubber, often smaller than the palm of your hand, is supporting the weight of the vehicle and transmitting all of the forces from the engine, brakes and steering to the pavement. Proper wheel alignment helps ensure all of those forces are going where they belong and the tires aren't being overworked.
While it may look to the naked eye like all of the tires are pointed straight ahead, they are all at slight but important angles. There are three different angles that affect wheel alignment: camber, caster and toe.
"Camber" is the degree to which a wheel departs from vertical (or perpendicular with the road), as viewed from the front. The top of each wheel is usually angled slightly inward. On an average car or truck, the angle is usually less than a few degrees, and you need special measuring equipment to determine the angle. The camber angle compensates for the way tire rubber stretches and deforms when cornering, and helps to make sure that the tire's contact patch remains in full contact with the road, including while going around corners.
"Toe" is the degree to which a wheel departs from being parallel to the other wheel on the same axle. If the front wheels (and the rears, if the vehicle has independent rear suspension) are angled slightly towards each other (as viewed from above) it's called "toe-in." "Toe-out" is when the wheels are pointing slightly away from each other. This is to counter the forces that push the wheels back into a more straight-ahead angle while driving.
Finally, "caster" is the frontward or rearward angle that the steering pivot point has from vertical, as considered from the side. The forces from the caster angle are what give the steering wheel a self-centering capability when you go down the road or relax your grip after going around a corner.
Each of these can be adjusted with links that are part of the suspension system. However, small variations in the angles can have a big effect on how the car drives and on tire wear. Sometimes hitting a big pothole or sliding into a curb can be enough to affect the toe or camber angle by a single degree or less, causing the vehicle to continuously pull in one direction or the other.
In addition to causing the vehicle to pull in one direction or the other, alignment problems also cause abnormally high, often uneven, tire wear. This can lead to a blow-out that could cause an accident, excess vibration that can be felt throughout the vehicle and reduced tire life.
Since checking and adjusting wheel alignment requires precision equipment, it should only be done by your dealer's service department. You should never attempt to adjust the alignment by hand at home. While most service facilities offer both front-wheel-only alignment and four-wheel alignment, it is usually best to go for four-wheel alignment.
On rear-wheel drive cars and trucks with a solid rear axle, there usually aren't any adjustments available for the rear wheels. However, even in this case, four-wheel alignment is important because the front wheels will be adjusted relative to the rear wheels so that everything is pointed in the right direction. Doing a front-only alignment can still leave the car pulling in one direction or the other.
One way to determine if your vehicle needs an alignment is to drive it down a straight, flat road with little or no crown (the fall-off toward the outer edge). The car should track straight ahead without you having to tug on the steering wheel. If the vehicle diverges from straight ahead without steering input, get it serviced soon.
You should also do a regular visual inspection of all four tires for uneven wear. The tread depth should be relatively consistent. You can quickly check the depth using a penny stuck into the grooves. If the top part of Lincoln's head is covered by the rubber in each groove, you have enough tread left. However, if the depth is significantly different on the inner or outer edge of the tire, you could have an alignment problem that needs to be corrected.
Most alignment work can be done quickly and often doesn't require any parts replacement unless the vehicle has hit something severe and bent a suspension link. A proper alignment and a regular tire rotation with each oil change will help your tires last longer and make your vehicle safer and more enjoyable to drive.
This article is presented by Land Rover Cincinnati, in Cincinnati, OH.