The function of "front wheel alignment" is to ensure the stability of the car driving in a straight line, turn easily and reduce tire wear. The front wheel is the steering wheel, and its installation position is determined by four items: kingpin camber, kingpin camber, front wheel camber and toe-in, which reflects the positional relationship among the steering wheel, kingpin and front axle on the frame.
The kingpin inclination means that the kingpin is installed on the front axle at a slightly inward inclination angle, and its function is to automatically position the front wheel. The bigger the angle, the stronger the automatic positioning function of the front wheel, but the harder the turning, the more tire wear; On the other hand, the smaller the angle, the weaker the function of automatic righting of the front wheel, so the camber angle of this kingpin has a range of about 5-8.
The caster angle of the kingpin refers to the angle at which the kingpin caster angle is installed on the front axle and the upper end of the kingpin tilts slightly backward. This is the same as the principle that the front fork of motorcycle leans backward, so that the direction of the moment formed by centrifugal force is opposite to the direction of wheel deflection when the vehicle turns, forcing the wheel to automatically return to the original middle position after deflection. Therefore, the greater the caster angle, the higher the vehicle speed and the better the front wheel stability. However, the large caster angle of the kingpin will also make it difficult for the driver to turn the steering wheel, so the caster angle of the kingpin also has a range, generally not greater than 3. Some tires are depressed and elastic. When driving, the center of the contact surface between the tire and the ground moves backward, which will also produce torque, so the caster angle of the kingpin can be reduced or even become negative, that is, the kingpin leans forward.
Both the inward-inclined kingpin and the backward-inclined kingpin have the function of making the steering of the automobile automatically return to the right side and keep driving in a straight line. The difference is that the alignment of the kingpin inclination angle has nothing to do with the vehicle speed, while the alignment of the kingpin inclination angle is related to the vehicle speed, so the alignment of the kingpin inclination angle is large at high speed and large at low speed.
The camber angle of the front wheel directly affects the turning performance of the automobile, and its function is to improve the steering safety of the front wheel and the portability of steering control. The camber angle of the front wheel is commonly known as the "outer contour". If the wheel is vertical to the ground and fully loaded, it is easy to deform, which may cause the upper part of the wheel to tilt inward and cause the wheel coupling to be damaged. So the wheel is offset by an abduction angle in advance, which is about 1.
Toe-in is a very familiar job for auto mechanics, and it is necessary to check the toe-in of wheels during auto repair. The so-called toe-in refers to the difference between the rear distance and the front distance of two wheels, and also refers to the included angle between the front wheel centerline and the longitudinal centerline. The toe-in of the front wheel is used to ensure the driving performance of the car and reduce tire wear. When the front wheel rolls, its inertia force will naturally deflect the tire inward. If the toe-in is appropriate, the deflection direction of the tire will deviate when rolling, and the wear inside and outside the tire will be reduced. Different cars have different toe-in adjustment values. The toe-in of the front wheel can be adjusted by the length of the tie rod, which will be explained in detail in the automobile manual.