by Jim Kerr
The installer had just finished bolting a new wheel aligner to our shop floor and was about to give a demonstration. The machine looked impressive – shiny red paint, glittery chrome, a large colour computer display, and flashing LED sensors made it seem more suitable for a disco club than an automotive shop. Do we really need this high-tech equipment just to check wheel alignment, or is it all smoke and mirrors?
Regular wheel alignments will usually save you as much in tire wear as they cost. A hard bump from hitting a curb or pothole can throw your wheels out of alignment and damage your tires. Front-end alignment, sometimes called two-wheel alignment, checks only the front wheel angles. This may be fine for old rear-wheel drive vehicles, but it doesn’t check if the front tires are properly positioned in front of the rear tires. To do this, you need a 4-wheel alignment, and that is what this fancy new wheel aligner I was looking at specialises in doing.
Four-wheel alignment checks the front wheel angles, the rear wheel angles, and the thrust angle alignment as well. Thrust angle alignment is checked so that the wheels are “squared” to each other. This eliminates the “dog tracking” that you may have seen on a car that appears to be going down the road with the rear end driving on a different track than the front.
Independent rear suspensions and front wheel drive have made 4-wheel alignments a must. Three angles are checked at each wheel – camber, caster, and toe. Camber is the inward or outward tilt of the wheel at the top. Its purpose is to provide directional control stability by placing the maximum tire tread in contact with the road surface under all conditions of vehicle operation and to prevent tire wear.
Caster is the forward or backward tilt of the steering knuckle at the top. The purpose of caster angle is to provide directional control stability of the wheels for travel in a straight course with minimum steering effort. It also assists in returning the front wheels to the straight-ahead position after cornering, but caster has no effect on tire wear.
Toe-In is when the front of the wheels are closer together than the rear of the wheels on the same axle. Toe-Out is when the front of the wheels are farther apart than the rear of the wheels on the same axle. Toe is the most important alignment adjustment on the vehicle for preventing tire wear. An incorrect toe measurement of 1/8 inch is equal to driving a car one-mile and having the tire dragged sideways eleven feet. Too much toe and the tread is soon scraped off!
Some vehicles have all the angles adjustable. Others require special adjusting kits or are non-adjustable, although toe angles are adjustable on almost all vehicles. Vehicles that are too far out of adjustment may have worn or bent parts. Part of any wheel alignment is a suspension inspection to identify worn or damaged parts. Getting an alignment with worn parts is a lot like jogging in running shoes 4 sizes too big – sure it can be done, but you are never sure which way the shoes will touch the ground.
Besides preventing excessive tire wear, a 4-wheel alignment also provides stable handling. If the wheel angles are wrong, then the vehicle can be unpredictable or twitchy during cornering or braking. This usually doesn’t show up on good road surfaces, but water or ice on the road can make driving your car more exciting than a roller coaster ride.
So how was our new alignment machine? Quick! Put a clamp-on adapter on each wheel, roll the car back and forth a few inches, turn the steering left and right, and all the measurements are displayed by the computer. I could have done the same with some simple tools and a level, but it would have taken several hours to do what this aligner did in 5 minutes. Not only did it show me the wheel angles, but bent suspension parts and even a twisted frame can be displayed. No wonder a 4-wheel alignment is required by many provinces when severely damaged vehicles are repaired and put back on the road. The alignment readings can pick out improper repairs.
After taking the readings, it still takes a few minutes to make adjustments and verify everything is good. Abnormal treadwear, a vehicle pulling to one side, or unpredictable handling are all symptoms of a vehicle that requires an alignment. An alignment can even make your vehicle roll easier, saving you money at the gas pumps. Make an alignment part of your vehicle’s routine, preventative maintenance. It pays in the long run.