Computerised 4 Wheel Alignment

What is Computerised Wheel Alignment?

Wheel alignment is important for good road holding and to maximise the lifespan of your tyres. Hitting a kerb or driving at speed through a pot hole can result in your wheels becoming misaligned. Incorrect wheel alignment can result in rapid wearing on the edges of the tyre and could affect the handling on the vehicle and certainly mean a replacement earlier than would otherwise be required.

How does it work?

What is camber?

Camber is the tilting of the wheels from the vertical when viewed from the front of the vehicle. When the wheels tilt outward at the top, the camber is positive. When the wheel tilts inward at the top, the camber is negative. The amount of tilt is measured in degrees from the vertical. Camber settings influence the directional control and the tire wear.

How does camber affect wheel alignment?

  • Too much positive camber will result in premature tire wear on the outside of the tire and cause excessive wear on the suspension parts.
  • Too much negative camber will result in premature tire wear on the inside of the tire and cause excessive wear on the suspension parts.
  • Unequal side-to-side camber of 1 degree or more will cause the vehicle to pull or lead to the side with the most positive camber.

Computerised Four Wheel Alignment measures a minimum of 12 angles and compares them to the alignment data specified by the vehicle manufacturer. Wheel rim run-out compensation is taken into account, which gives accurate and repeatable readings. With such accurate readings, Four Wheel Alignment allows toe adjustments of individual wheels which ensure the steering wheel is set straight.

Further adjustments of camber, caster and other angles (where necessary) can ensure optimum performance and savings. A print out, of before and after is given on the most modern Wheel alignment machines just like ours.

How does caster affect wheel alignment?

  • With too little positive caster, steering may be touchy at high speeds and wheel returnability may be diminished when coming out of a turn.
  • If one wheel has more positive caster than the other, that wheel will pull toward the center of the vehicle. This condition will cause the vehicle to pull or lead to the side with the least amount of positive caster.

What is caster?

Caster is the tilting of the uppermost point of the steering axis either forward or backward, when viewed from the side of the vehicle. A backward tilt is positive and a forward tilt is negative. Caster influences directional control of the steering but does not affect the tire wear. Caster is affected by the vehicle height, therefore it is important to keep the body at its designed height. Overloading the vehicle or a weak or sagging rear spring will affect caster.

When the rear of the vehicle is lower than its designated trim height, the front suspension moves to a more positive caster. If the rear of the vehicle is higher than its designated trim height, the front suspension moves to a less positive caster.

What is Toe?

Toe is a measurement of how much the front and/or rear wheels are turned in or out from a straight-  ahead position. When the wheels are turned in, toe is positive (+). When the wheels are turned out, toe is negative (-). The actual amount of toe is normally only a fraction of a degree. The purpose of toe is to ensure that the wheels roll parallel.

Toe also serves to offset the small deflections of the wheel support system that occur when the vehicle is rolling forward. In other words, with the vehicle standing still and the wheels set with toe-in, the wheels tend to roll parallel on the road when the vehicle is moving. Improper toe adjustment will cause premature tire wear and cause steering instability.

When a pair of wheels is set so that their leading edges are pointed slightly towards each other, the wheel pair is said to have toe-in. If the leading edges point away from each other, the pair is said to have toe-out. The amount of toe can be expressed in degrees as the angle to which the wheels are out of parallel, or more commonly, as the difference between the track widths as measured at the leading and trailing edges of the tires or wheels. Toe settings affect three major areas of performance: tire wear, straight-line stability and corner entry handling characteristics.

How does Toe affect wheel alignment?

For minimum tire wear and power loss, the wheels on a given axle of a car should point directly ahead when the car is running in a straight line. Excessive toe-in or toe-out causes the tires to scrub, since they are always turned relative to the direction of travel. Too much toe-in causes accelerated wear at the outboard edges of the tires, while too much toe-out causes wear at the inboard edges.

Why not cheaper Tracking / Laser Alignment Methods?

In its original sense, Tracking uses gauges (usually the hang-on style) where the operator peers through a ‘scope’ or views a light/laser beam on a scale. This system does not allow for run out compensation (taking account for any errors in the wheel rim), so the reading result can only at best be approximate.

Tracking was born of a bygone era, when cars had very little or no adjustment. Any measurement and adjustment tended to be on the front wheels, for the ‘Toe’ angle only. On modern cars, tracking alone is unlikely to deliver complete alignment or complete customer satisfaction.

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