Correct wheel alignment ensures that the rear wheels follow in the same tracks, the front wheels make. Having your alignment checked regularly can extend your tyre life by upto 10 000km. We recommend that your wheel alignment is checked every 10000km.
Improper Wheel Alignment causes the vehicle to pull to one side, reduced tyre life and possible damage to your cars suspension system.
In order to achieve accurate tracking (when the rear wheels follow the same tracks as the front), it is essential that all four wheels are taken into account. As vehicles can easily be steered by the rear wheels unless they are pointing directly towards the front wheels.
Incorrect alignment will steer the rear in the direction of the thrust line when the front wheels are in the straight forward position, causing the front of the vehicle to veer off in the opposite direction and the vehicle moves along in a crab-like fashion.
When all four wheels are referenced during a four-wheel alignment, the thrustline can be adjusted by setting the rear toe. On vehicles that have no rear toe adjustment, the modern alignment machines are able to compute the rear thrust-angle and provide revised values for the front toe settings which results in all four wheels tracking correctly. This does not stop the vehicle from crabbing but at least all the suspension angles will be correct and the steering-wheel will be level.
Tyre wear due to incorrect alignment
Alignment refures to the suspension angles on the vehicle. There are three main criteria this sort of tyre wear, they are toe, camber and castor.
Excessive toe angles (positive or negative) are the major cause of rapid tyre-wear. This is easy to understand when one realises that the wheel is dragged sideways by the amount of toe every time the wheel makes one rotation.
A vehicle that has a total front toe reading of + 4mm means that, as soon as the vehicle moves forward, each front wheel will "toe in" by 2mm. This means that the tyre is "dragged" inwards or across the direction in which the vehicle is travelling by 2mm with each revolution.
Front toe is adjustable on all vehicles.
Rear toe adjustment is becoming more common and it will be noted that few rear toe specifications call for the use of negative rear toe. It is desirable for the rear toe to be slightly positive because it provides stability under braking and creates understeer tendencies in cornering.
Camber is also a tyre-wearing angle, but not as severe as toe.
It is defined as positive when the top of the wheel tilts away from the vehicle centre-line. This means that because the outside shoulder of the tyre carries more load than the inside shoulder, excessive wear will take place on the outside shoulder.
Negative camber is when the top of the wheel tilts towards the vehicle centre-line. In this instance the inner shoulder is working harder than the outside and will therefore wear at a faster rate. A negative camber of between one quarter and half a degree does not cause excess wear but enhances road holding.
Camber wear has a tendency to be "smooth" and is noticeably different from the distinctive "feathered" wear caused by excessive toe.
Camber is adjustable on some vehicles.