To put it simply, the angle of inclination is the angle of the wheel relative to the surface. Alongside the overall wheel alignment, it is one of the most important aspects of geometric diagnostic workshops. This is rightly so, since the car camber is responsible, to a very large degree, for the correct positioning of the wheel on the road. This, in turn, influences the tyre’s contact patch on the road, changing the effectiveness of your tyre grip.
The best way to understand a wheel camber is to imagine a freely rolling wheel. It is clear that such a wheel will have the greatest contact patch with the road surface when it is exactly perpendicular to the road itself. This angle is called zero camber.
In practice, this is assuming that the wheel is rolling freely and does not turn. In reality, however, you also have to account for the suspension arm, which may transfer its load onto the wheels, influencing the camber. Aside from the zero camber, the angle can be negative if the top of the tyres/wheels are turned in towards the vehicle, and positive if they instead point outwards.
When a vehicle handles a corner, the centrifugal forces acting on it are balanced by the forces resulting from the tyre’s grip. The greatest effect on grip comes from pressure, as a reduction in pressure means a loss in grip. Due to the centrifugal force, however, the pressure exerted by the tyre on the road is greater on the outside of the tyre than it is on the inside. This means the tyre is unevenly loaded and is not exploiting the full potential of its grip. For this same reason, tyre deformation may occur eventually.
A solution to such situations involves tilting the wheel at a negative camber angle. This will lead to higher pressure on the inside of the tyre and lower pressure on the outside. When the centrifugal forces take effect on a corner, there will no longer be such a great reduction of inside pressure, as compared to a perpendicular tyre.
Based on the current assessment, we can clearly see that the direction and angle of the inclination matter, with slightly negative being better than a zero camber or positive camber. However, the value of this angle is an important factor, too.
Any angle other than zero camber (neutral camber) will cause wear and tear on the tyre when driving in a straight line. This is because the tyre is still angled, creating an un-uniform contact patch. For this reason, vehicle design engineers have to make a compromise between the road camber’s benefits when turning and the damage it would cause to the tyre when going straight.
This, in essence, is a game of moderation, with a goal towards creating a uniform load on the tyre where possible. If the wheel is inclined too much, the outer edge will be at a too wide angle to grip the surface. This will also put pressure on the tread’s inner side, causing noticeable tyre damage.
In the case of a positive camber, the car will already have a load on the outer edge of the contact area between the wheel and the road before it comes across a turn. When facing the centrifugal forces while turning, this additional load may cause the tyre to be overloaded (marked in red on the illustration below). That, in turn, may result in the tyre wearing out more quickly. Furthermore, the vehicle does not make full use of the available grip on the tyre surface, only using a part of it as a result.
The value of the camber angle, specifically the angle of the wheels in relation to the road surface, are directly linked to the vehicle’s height. As a result, any reduction in height will always affect these related values.
In a small car with a front suspension system - based on MacPherson struts - lowering the vehicle by just 25 mm can increase the camber from –0.3° to –0.6°. Yet, in other cases, a reduction of 60 mm has only resulted in a change of –1° in terms of camber angle values. For this reason, after applying any alteration to your car’s height, you should always check that the geometry remains within the permitted range.
Such effects and changes should not be neglected, especially since most popular car models with MacPherson suspension do not provide any possibility of adjusting these parameters. The only solution in these cases is to fit a special suspension system with camber plates, enabling movement of the upper point of attachment.
If you drive with too large a camber angle, you will experience a number of effects. The first, although not the most important, is the damage suffered by the tyre’s contact surface on the inner-facing parts. If left unchecked, this will deteriorate below the legal limit for tread depths, which can result in the vehicle’s registration documents being confiscated during a police check.
Furthermore, the vehicle will behave more dramatically during turning. This is because of the failure to achieve the optimum distribution of tyre pressure. From the driver’s perspective and experience, this will result in a noticeable loss of grip.
All in all, car camber is a very important element of car suspension. It influences a wide range of driving and safety factors. So if, for whatever reason, you decide to apply any modifications to your camber, remember to be careful, take all the necessary factors into consideration and check every alteration thoroughly.