Camber is probably the most useful and popular alignment adjustment that can be made to a street car. The other alignment adjustments are toe and caster, which I have covered in accompanying articles. Camber is the angle of the wheel from the vertical as viewed from the front or the back of the car. Negative camber means that the top of the wheel is leaned in towards the car, and positive camber means that the top of the wheel is leaned out away from the car.
Maximum cornering force is achieved when the camber of the outside wheels relative to the ground is about -0.5 degrees. A slight negative camber in a turn maximizes the tire contact patch due to the way the tire deforms under lateral load. Hence, it is good to have some negative camber to increase cornering force.
Another reason why it is helpful to align your suspension with a slight negative camber is that camber will change with suspension travel and body roll. Most suspension systems are designed so that camber increases with more suspension travel. However, camber relative to the car’s chassis is not the same thing as camber relative to the ground. It is camber relative to the ground that affects handling.
Therefore, even though camber relative to the chassis is made to increase, camber relative to the ground may actually decrease on the outside wheels if there is substantial body roll. To counter this tendency, it is important to use negative camber and to control body roll.
The only drawback to negative camber is increased wear on the inside of each tire. Since the top of the wheel is leaned in, the car is riding on the inside of the tire while it is on straightaways. In a corner, suspension travel and lateral forces on the tires rubber compound combine to straighten the tire relative to the ground. Therefore, the car rides evenly on the tire in turns, which improves cornering ability. However, extra time spent driving on the inside of the tire causes that part of the tire to heat up and wear. This effect is small if you avoid adding too much negative camber.
On most street cars (which use a MacPherson Strut front suspension), camber is not easily adjustable. However, if you choose to purchase aftermarket camber plates, you can set camber to improve handling. More negative camber tends to increase tire grip in corners. Therefore, if your car experiences understeer, you can decrease front camber (make it more negative) to improve front grip or increase rear camber (make it more positive) to decrease rear grip. Remember not to add too much negative or positive camber since it will decrease the life of your tires and may cause a blowout. Even pure race cars rarely use more than about 3 degrees of camber. As with any adjustments, make camber changes in small increments, and make sure to test the setup so that you can see the results from each specific change.