As with toe, zero camber (perfectly perpendicular to the road) is the ideal alignment setting. But like toe, camber changes as the vehicle is being loaded and every time the vehicle encounters a bump or dip in the road. The up and down motions of the suspension change the geometry of the control arms and struts, which causes camber to change. So many static camber alignment specifications may allow up to a degree of more of positive or negative camber depending on the design of the suspension. As a rule, camber settings should usually be within half a degree side-to-side.
Camber refers to the vertical tilting of a vehicles wheels when seen from the front of the car. If the wheels tilt outward at the top of the tire, the camber is referred to as positive. If the tire tilts inward, then the camber is called negative. A camber alignment aligns the camber of the wheels so they are parallel to each other.
If camber is out of specs, a tire will wear unevenly on one shoulder and the vehicle may pull toward the side with the most camber. Camber usually only affects one wheel, so if only one tire shows unusual shoulder wear it is usually a symptom of camber misalignment.
Keep in mind that camber applies to both front and rear wheels, though only vehicles with independent rear suspensions typically have rear camber alignment specifications. Most rear-wheel drive cars and trucks with solid axles do not have rear camber specifications because there's no way to change it (even so, a bent rear axle can cause a camber problem!).