At Hawleys we use the very latest Laser Technology to ensure ultimate accuracy when checking or adjusting your vehicles steering and suspension geometry. All our Technicians are specially trained to ensure maximum benefits are gained by the customer in terms of safety, tyre, steering and suspension component wear.
Shown below are some of the adjustable settings and why they are important.
The easiest and most obvious part of steering setup is the tracking or `toe-in/toe-out' settings. This is the directional alignment of the front wheels. A common fallacy would be to expect the wheels to be parallel, both pointing in the same direction. In reality the majority of cars, will have the wheels pointing ever so slightly in different directions. Often this amount is so small that it cannot be seen by the naked eye. This measurement is known as the 'toe' and is measured by taking the distance across the car at two points on the wheel, ideally halfway up the tyre. The measuring can be done on either the inside or the outside of the wheels and you can often see different devices being used to do this quickly and easily. When the wheels point outwards at the front, you have a toe-out set-up and the obvious reverse when the wheels point inwards, is toe in.
Vehicle manufacturers specify different settings for different models, even from generically the same vehicle but a different specification. Therefore it is most important that the correct settings are obtained for each vehicle and carefully applied.
The second part of wheel alignment is the angle at which the wheel sits on the road, which is known as camber. The amount of camber that is required will depend on many things, the vehicle type, tyre width and side wall strength, car speed and use will all have an effect. Camber is measured in degrees away from the vertical. Many vehicle manufacturers use what is known as centre point steering. This aligns the line drawn between the top and bottom suspension pivots and the centre of the tyre contact area, thus providing stability, feedback through the steering wheel and hence greater safety.
Another important part of wheel alignment is the alignment of wheels in respect to each other across the car. For many cars there will be a fixed axle either at the front or rear of the car, sometimes both. The exception to this will be cars that have independent suspension all round, which allows the alteration of the fore and aft position of the wheel without any other wheel. This is now common on modern vehicles and it is increasingly important that the geometry of all four wheels is correctly set.
The final thing to note about wheel alignment is that when the car is moving, there are dynamic forces caused by acceleration, braking and body roll, that can change some of the settings. It is therefore most important that all the vehicles wheels are correctly set to the manufacturers recommended settings.
The final part of wheel alignment is to do with the steering axis. The steering axis is the point around which the wheel pivots when the steering is turned. On some cars it will be around the suspension strut, on others where the upright bolts to the wishbones or front axle. In either case, it is the vertical alignment of the top and bottom of this axis that determines caster. On most cars the bottom end will be further forward than the top, giving positive caster. This creates an effect like the wheels on a shopping trolley. If it is pushed forward the wheels will centre themselves, pointing in the direction of travel.
The greater the angle of caster, the stronger the centring force, which effectively means heavier steering. With a low caster angle the car will be more willing to go around the corners, but the counter effect is that is will be less willing to straighten up afterwards. If a car is given too much caster, i.e. the bottom of the steering axis is further forward than the top, the steering will be very heavy and the car will be reluctant to turn into a corner. Conversely, if the car were to be given negative caster, with the lower end of the axis further back than the top, there would be no directional stability at all. The car would need constant steering adjustment to keep it in a straight line.
