Driving along a scenic road in a great car is a pure pleasure – a harmonious blend of sophisticated precision machine, speed and human control. For a car to perform perfectly, however, its suspension geometry – the important angles between the wheels and the axles – must be correct.
The gradual wear and tear of everyday driving can start to knock these angles out of alignment. One of the main causes is driving over potholes, especially at high speed, or clipping a kerb. Speed bumps can also cause problems. Even bodywork repairs involving the front or rear axle can modify the wheel alignment or other ride values.
So it is important to check three main aspects of a car's suspension geometry when maximising that vehicle's performance:
• tracking – also known as toe – which measures whether the front of the tyres are closer or further apart than the rear of the tyres on the same axle
• camber, the vertical tilt of the tyres relative to the ground
• caster, the backward or forward inclination of the suspension system.
Tracking, which is the most important of these factors, is a measurement (normally in millimetres) of the angle of the wheels on the same axle with respect to the longitudinal centre line of the vehicle. If the fronts of the wheel rims are pointing towards each other, then they are said to be toe-in. If they point away from each other, then they are toe-out.
In reality, although the difference is invisible to the naked eye, wheels are not normally perfectly parallel with one another and are slightly toe-in. This alignment is designed to compensate for the temporary warping created in the geometry of the suspension as a result of the stresses created through the car when it is braking, accelerating or cornering.
The phenomenon occurs to a greater extent on production cars, which are designed for comfort and have their suspension mounted on rubber blocks for added elasticity. When braking, all the wheels tend to open out, for example, while the driving wheels tend to close in during acceleration, especially on cars with front-wheel drive, which dominate the market.
The signs that a car needs to have its wheels measured and balanced are relatively easy to spot. If the steering wheel pulls to the left or right on a pristine strip of Tarmac, for example, it's time to visit the experts. So, too, if an unusual vibration is felt through the steering wheel, although this can be caused by a variety of other issues.
Tread wear at a very uneven rate across the width of the tyre is also a symptom. Excessive toe-in causes understeer during cornering and the tread will begin to wear from the outer side. Toe-out causes oversteer and greater wear on the inner side of the tyres. By running your hand over the tyre tread it is possible to feel for irregular patterns. If in doubt, it's best to get the car checked.
The good news is that once the wheels are in perfect alignment you will notice the difference straight away. Your car’s steering will feel smooth and effortless once again... just like the day you first drove it out of the garage.