While the eye-catching tuning phenomenon known as “demon camber” or “hella flush” doesn’t provide much in the way of performance – in fact it hurts it – its extreme styling brings the viewer’s eyes into relation with the concept of camber, something which evades casual drivers and even a few petrolheads.
In learning a bit about how camber works, its role in tire wear, cornering performance, ease of adjustment, and the limitations various suspension designs have when it comes to camber, any car’s handling can be quickly optimized for a reasonable cost.
What Is Camber?
Camber is the angle at which the wheel and tire stand relative to the road – assuming it is perfectly flat. The easiest way to envision what camber looks like is to view the wheel and tire head on. When stationary, the tire maintains a static camber angle, whereas when the car is cornering, due to body roll, the contact patch is reduced. In order to counteract this effect and have the greatest amount of tire on the road while cornering, camber settings must be taken into consideration and adjusted accordingly.
While conventional thinking might lead one to believe that the wheel is perfectly perpendicular to the road on which it sits, it is often intentionally tilted slightly to counteract the forces imparted on it by cornering. If the top of the tire is leaned in closer to the center of the car, that particular wheel and tire exhibit what is called negative camber. Positive camber, on the other hand, has the top of the wheel pointed outwards. While this article delves into the merits of negative camber, there are benefits to some positive camber in racing as well. However, this situation is typically isolated to circle track racing where cars run on banked race tracks.
How Does It Work?
Negative camber is the characteristic generally desired in performance driving. When we use the term, we’re referring to static negative camber. That is, the wheel and tire should exhibit some negative camber while sitting. When you barrel into a corner, the laws of physics have you, the wheels, and the tires pushed toward the outside of the corner.
When the wheels and tires are pushed outwards and the car’s body rolls, the contact patch, or the area of the tire which comes into contact with the surface of the road, diminishes significantly as it rolls over onto its outer shoulder.
Negative camber is implemented so that when the car is cornering and the wheel is rolling over and gaining positive camber (from body roll, not suspension travel), the static negative camber should correct whatever effect leaning and lateral load have on the wheel and tire; resulting in a near-upright tire and the greatest possible contact patch.
Simply put, negative camber helps counteract the natural tendency for a tire to roll onto its outer shoulder while cornering, keeping the contact patch squarely on the road while cornering allow for more grip and higher cornering speeds.
There are some reasons that your car likely did not roll off of the showroom floor with optimum camber for the track. Too much negative camber causes the car to tramline or follow cracks or imperfections in the road, and also have an excessive sensitivity to the road’s crown (an engineered curve that promotes water drainage on roads). It also isn’t very friendly to tires, causing them to wear at a significantly higher rate. As a general rule, a car that’s sole purpose is commuting should have minimal negative camber – unless you don’t mind replacing tires regularly.
How Much Is Too Much?
How much negative camber do you want? It depends on what kind of suspension setup your car has. Cars with MacPherson struts need a significant amount of static negative camber because they have only a moderate camber gain under compression, when compared to a car with unequal-length control arms. When combined with the effect of body roll, the end result is usually less negative camber than desired, therefore requiring the addition of extra static camber. Cars with unequal length A-arms or multi-link suspension do not exhibit this shortcoming; they’re engineered to have a faster, more progressive rate of negative camber gain during cornering.
Determining Optimum Camber Settings
Determining what camber setting yields an evenly-applied contact patch can be done through measuring the heat at the inside, the center and the outside of the tire’s contact patch. By using a specialized thermometer called a pyrometer one can determine if one side of the tire is being heated more or less than the other. While you may be tempted to use a non-contact thermometer it only provides the surface temperature of the tire, which can be misleading. Rapid cooling of the tire and a disproportional effect of the last turn or turn the car has just driving doesn’t provide a record of how the tires were operating across several laps, the way a pyrometer can.
Generally speaking, there can be a difference of as much as 20 degrees F across the face of a properly aligned tire. If the inside is exceedingly hot and wearing faster than the outside, there is too much negative camber. When this is present with the front wheels, the effect is diminished braking capability, poor turn-in and pronounced mid-corner understeer. When the rear tires exhibit too much negative camber, the effect is oversteer and a reduced ability to accelerate cleanly out of corners.
The opposite, excessive positive camber, shows up as a reversal of the aforementioned temperature spread. The outside is excessively hot and wears much faster than the inside of the tire. This leads to understeer mid-corner after the car has made its initial turn, and is usually the result of too much roll. It is because of this that excessive roll must be limited with anti-roll bars.
What it really comes down to is driver feel and lap times. Tire temperature alone is not a sufficient data source to determine all suspension settings, but rather a tool that can be applied with other data to develop the most efficient and effective setup.
How Do I Adjust Camber?
To make adjustments to a MacPherson-suspension car, adding camber plates is a safe, easy and cost-effective way to doing it. Camber plates use an adjustable top mount which relocates upper shock mount to a retainer plate which slides laterally on a grooved track. Because the strut attaches directly to the hub, adjusting camber from the top mount is possible. Simply slide the adjuster toward the center of the car for increased camber or outward for less.
This is an attractive approach to adjusting camber especially if you autocross/track your car and want one camber setting when battling the clock, and another when driving home on the freeway.
Camber bolts are another cost effective way of adjusting camber easily, and in some cases, are the only way based on the class rules under which you may be running. Camber bolts are eccentric, meaning they have an off-centered lobe which alters the horizontal position of the knuckle slightly from the strut, therefore changing the camber angle. Camber bolts are also referred to as “crash bolts” because they are used to align cars which have been bent in an accident. Due to their design, they’re thinner than standard bolts and can be weaker. For that reason, it is important to make sure camber bolts are of high quality and sourced from a reputable manufacturer.
For cars with a multilink or unequal length A-arm setup, the shock/strut does not directly control camber. In order to change the camber on cars with these suspension setups, there are one or two possible ways to adjust the setting. One, the mounting points of one control arm need to be moved. This is often accomplished on factory suspensions by rotating an eccentric bolt that carries the control-arm-to-chassis mounting points. Or two, the length of one (or both) of the control arms need to changed. Be warned that altering the length of either of the control arms significantly will affect camber gain during suspension travel in addition to static camber. Keep in mind that every change in setting in your car’s suspension effects every other suspension setting.
If the car in question doesn’t have an adjustable upper control arm or upper control arm mounts provided from the factory, nor is there an aftermarket adjustable upper control arm, sometimes shims can be used behind the control-arm-to-chassis mounting point to adjust the camber, often seen in older vehicles.
For anyone seriously considering the performance potential or their car, camber is something that should not be overlooked. The feeling of increased grip and poise mid-corner is something that is sure to plaster an ear-to-ear grin on anyone’s face. Because most street cars are not designed with the race track in mind, their camber settings are somewhat conservative to ensure even tire wear in normal driving conditions.
Minute camber adjustments can make a standard car significantly more agile. As we’ve learned, when considering suspension adjustments it’s important to take into account your suspension design, but more importantly; use a scientific approach to determining what kind of camber is appropriate for your car. Though adding some negative camber will allow for higher cornering speeds and a more progressive feeling at the limit of adhesion, it can lead to premature tire wear, whereas improperly adjusted camber can result in instability and reduced traction.
Don’t let that prevent you getting out there and experimenting as it’s fun and educational and provide you a better sense of control over your vehicle.