The term camber actually has several different meanings, depending on the engineering principle involved. When it comes to bridges, roadways or airplane wings, it is the amount of curving or arching used to counteract the effects of a load. When a number of heavy trucks cross over a bridge at the same time, if there was no camber, the center would sag, then spring back to level when the trucks leave. By adding a slight upward curve, engineers can ensure that the bridge only flattens out to a level position when weight is added.
In the case of an airplane wing, camber is used to create lift and counteract the effects of drag. Looking at a cargo plane's wing from the front, an observer might notice an upward curve. Once the fully-loaded plane leaves the ground, the weight of its body exerts a downward pull on the wing. Since the wing is curved, this pulling force only causes the wing to level out, not to sag under the load.
The most common example that most people encounter every day is tire alignment. The three elements of a balanced tire are toe, caster, and camber. Toe is the inward or outward direction of a tire as viewed from the front. Caster is the position of the tire's center as it relates to the axle, either forward or back. Camber is measured as the degree of deviance from a 90° perpendicular alignment. In other words, negative camber means the tops of the tires lean towards each other, while positive means the tops lean away from the center.
People might assume that the ideal camber for a passenger car's tires would be a perfectly straight alignment. In actuality, many car experts recommend it be slightly negative for better control through curves. The slight inward bend allows the tires to counteract the effects of centrifugal force while driving through a turn. Professional stock car drivers often use positive camber on the right side tires and negative on the left side to improve handling in and out of left turns.
Improper camber alignment can lead to dangerous uneven tire wear, so it is important for vehicle owners check all four tires to make sure they are aligned correctly.