Wheel alignment is the adjustment of the angles of the vehicle's front wheels relative to the ground. Incorrect wheel alignment affects not only the handling of the car, but also tire wear. The installation of the front wheels is characterized by the following angles: the angle of spread, the angle of the longitudinal inclination of the kingpin and the angle of convergence (pic. 22.1). The angle of inclination of the kingpin and camber can be adjusted within a small range by moving the upper support of the suspension strut. The angle of convergence is adjusted by rotating the tie rod ends. The only rear wheel adjustment is toe angle adjustment. Other angles are measured only to check for deformation or wear of the rear suspension components.
Wheel alignment is a very important process that requires special equipment. However, we have provided information here that contains the basic principles of adjustment to help you better understand the process.
Toe-in - the difference in the distances between the inner surfaces of the wheels, measured front and rear at axle level. The purpose of this adjustment is to keep the front wheels parallel when the vehicle is moving. In a car with zero toe-in, the distances between the surfaces of the wheels in front and behind will be equal. Typically, the convergence value is a few millimeters. The toe-in of the front wheels is adjusted by turning the tie rod ends. The toe-in of the rear wheels is controlled by the cam device of the rear transverse levers. Incorrect toe-in adjustment results in increased tire edge wear and erratic vehicle movement in straight-line driving.
Camber - the angle at which the plane of the wheel is deflected from the vertical (looking at the wheel from the front). Positive camber is when the top edges of the wheels are further apart than the bottom. Camber angle is measured in degrees. This angle affects tread wear and compensates for changes in vehicle position on the road when cornering or over bumps.
Longitudinal inclination of the kingpin - the angle between the axis of rotation of the steered wheels and the vertical, when viewed from the side of the car. "Positive caster" means that the top point of the pivot axis is shifted back.