The vehicle industry has developed rapidly over the past ten years. The automobiles manufactured today are among the safest to ever have been driven in history. These vehicles are fitted with impressive pieces of technology including anti-lock brakes, drive by wire (DBW), vehicle skid control (VDC) and steer by wire (SBW) technologies. All these features end up being of profound help to automobile owners and mechanics alike when the vehicle comes in need of wheel alignment. Wheel alignment refers to the resetting or adjusting of the faculties of the vehicle’s wheel angles to the specifications of the manufacturer. Vehicle wheels may lose their alignment due to accidents, steering or suspension repairs or tire replacement due to wear and tear.
Wheel alignment requires for the wheel angles to be parallel to one another and perpendicular to the road to facilitate level steering drive and preserve tire life. There are several angles that are adjusted during the wheel alignment process, they include the caster angle, camber, toe and thrust angle. Caster refers to the angel of the steering axis to the fore wheel. When the axis leans beyond the fore wheel the caster angle is negative and when it leans behind the wheel (toward the steering) the caster angle is positive. The effective range of caster is between 3 and 5 degrees positive, these degrees may be lower for heavier vehicles in order to reduce steering efforts.
The camber angle is the tilt of the wheel in or out of the car. When the top of the tire is aligned to tilt outwards the camber is defined as positive and the opposite is true. The camber angle may be lost in a car as a result of an accident of the vehicle that damages the strut and spindle assembly, or due to the sagging of the vehicle springs of or even wear and tear of the ball joints. A derangement of the camber places the tire incorrectly against the road causing it to wear out prematurely and on one side. The camber angle is very complex to control as there are many factors affecting it including the speed of the vehicle which causes aerodynamic forces to change the riding height. Even after repair, camber angles may continue to prove problematic due to the uneven roads causing uneven contact between the tire and the road.
Changes in the camber does affect the toe directly. Toe refers to the angle of the wheel against the ground surface. When the front of the tires point inward, as if to face each other, the wheels are described as having a positive toe while if they face the opposite directions they are described to have a negative toe. The toe angle greatly affects tire life the ideal alignment for maximum durability being perfectly perpendicular to the road. However tire life is sometimes sacrificed for optimum vehicle performance. A positive toe provides the vehicle with a better straight line tracking but at the expense of its turning ability. For this reason most front tires are aligned to have a slightly negative toe while the rear wheels are given a more positive toe all which align themselves parallel to the road at high speeds.
The thrust angle refers to the angle of the rear wheels in relation to the vehicle’s symmetrical axis. One experiences ‘dog tracking’ when the thrust angle is not at zero as the back wheels are not centered. This is corrected by adjusting the rear toe first. It is aligned to the center line succeeded by a subsequent adjustment to the fore toe turning it to correspond to the rear. If the vehicle does not allow rear toe adjustment then the alternative is to align the front toe to correspond to the thrust error in the rear and regain the steering center.
Before a manufacturer releases a vehicle from the plant, a series of tests, researches and conclusions have been made to come up with a good performing motor vehicle. A considerable amount of time and resource is used to come up with the appropriate balance of assembly, coordination, stability and handling attributed to a good car. Once the car begins its use on the road it immediately starts losing its original balance. It is the responsibility of the owner to constantly restore this balance for optimum performance and longevity of the automobile.