Wheel alignment is the process of positioning the wheels correctly so that they are in the right angular position to the suspension and the ground which is essential to vehicle control and tires wear reduction. The main angles that are measured in the course of this procedure are camber, caster and toe-in. Although camber and caster are not always adjustable, they are usually inspected during wear or damage in the wear component of the suspension parts. The toe-in, the inward angle of the wheels can be adjusted on the front of all cars, and on the rear of cars with independent rear suspension, so that the wheels roll parallel. A car that has a zero toe-in would have the same distance between the front and rear edges of the wheels and even the slightest wrong toe-in would result in inappropriate tires wearing. The inclination of the wheels relative to the vertical is called camber where positive camber means a tilt outward at the top and negative camber a tilt inward. The camber is expressed in degrees, and affects the tread contact on the road of the tires, and compensates the variation in the geometry of the suspension when turning a corner, or when traversing an uneven surface. Caster identifies the tilt of the front steering axis with a positive caster having a tilt of the front steering axis toward the rear and the negative caster having a tilt towards the front. The alignment of the wheels involves specialized tools and skill hence there is an advantage of having a skilled technician to do the adjustments.