Four wheel alignment parameters
Four wheel alignment parameters
Many merchants only adjust the front when positioning the car owners. In fact, there are many parameters to be adjusted for the four-wheel alignment.
Four wheel alignment related parameters include: caster caster angle, kingpin camber angle, wheel camber angle, toe angle, tolerance angle, propulsion angle and friction radius.
1. Camber angle: The angle between the geometric centerline of the tire and the plumb line on the ground, viewed from the front of the car, is called the camber angle. The upper edge of the tire is either on the inside (near the engine) or on the outside (offset from the engine).
When the tire centerline coincides with the plumb line, it is called zero camber and its function is to prevent uneven wear of the tire.
The angle between the centerline of the tire and the outside of the plumb line is called the positive camber angle. Its function is mainly to reduce the load acting on the steering knuckle, prevent the wheel from slipping, prevent the unnecessary camber due to the load and reduce the steering. Manipulating power.
When the center line of the tire is inside the vertical line, the angle is called the negative camber angle. The function is to make the inner and outer rolling radii approximately equal, so that the inner and outer sides of the tire are evenly worn, and the lateral stability of the body can be improved.
The adjustment of the camber angle varies depending on each model, and the adjustment method is also different. The main adjustment methods are: adjusting the gasket, the beam slot, the different center cam, the eccentric ball head, the adjustment of the upper control arm, and the adjustment of the lower control arm.
2. Front toe: The front toe is measured from the front of the vehicle and measured under the same height of the two axles. The difference between the front and rear ends of the centerline of the left and right tires is called the total toe.
The role of the toe is to eliminate the tire slip due to the camber angle.
When the front toe is too large, the outer wear of the tire has a wear state formed by a large camber angle, and the tread wear form is feathery. When the hand is stroked from the inside to the outside, the outer edge of the tread has a sharp feeling of stabbing.
When the negative toe is too large, the inner side of the tire will have a wear pattern formed by a large negative camber angle, and the tread wear form is feather-like. When the hand is stroked from the outside to the inside, the outer edge of the tread has a sharp tingling sensation.
Adjusting the front toe of the front wheel: Adjust the adjustable lever. Before adjusting, loosen the ball and pin bolts on the left and right sides to clamp the center of the steering wheel. Then adjust according to the information provided by the computer. If the original steering wheel is in the center position, adjusting the toe steering wheel at the same time may not change. Until the standard value is adjusted, then the road test will see if there is any change, and if there is any change, it should be adjusted.
3. Caster caster angle: The angle between the upper ball head or the top end of the strut and the lower ball head (assumed steering axis) is inclined forward or backward from the side of the vehicle, that is, the angle between the steering axis and the vertical line of the ground. The caster angle includes three types: a positive caster angle and a negative caster angle and a zero caster angle.
The function of the caster back rake angle is to reset the wheel and improve the stability of the straight running. The resulting positive return torque enables the car to automatically return to the steering wheel of the car to set the caster angle when the vehicle encounters an external force during driving.
The main function of the caster angle is to keep the vehicle moving straight ahead. The angle of the caster does not affect the tire grinding. It is used to stabilize the direction of the car and to automatically return to the steering.
For the adjustment of the back-tilt angle, it should be analyzed and judged according to the different models, and then adjusted. The adjustment methods are as follows: gasket, camshaft of different hearts, eccentric ball head, beam slot, balance bar, etc.
4. Inward angle: The angle formed by the steering axis from the front of the car and the plumb line on the ground.
The function of the internal inclination angle is to reduce the steering force, reduce the rebound and deviation, and improve the stability of the vehicle in straight running.
The definition of four angles and the functions of each angle are relatively easy to understand. However, the application of the four wheel alignment and chassis maintenance is often unable to solve the problem. The reason is that due to the structure of the chassis of the vehicle body, all four wheel alignment angles are connected to each other through the mechanical structure of the chassis. For example:
(1) Changing the toe angle will change the camber angle: the wheel will change according to the steering axis when the toe angle is changed, so the camber angle will change. The greater the caster angle, the greater the change in the camber angle.
(2) Adjusting the back tilt angle will change the wheel yaw angle: When the back rake angle is increased or decreased, the fulcrum on the steering shaft can move forward or backward. The other thing that can be moved is the lowest fulcrum of the steering shaft, which is the tire. Therefore, increasing or decreasing the adjustment of the caster angle causes the front wheel to slide forward or backward, and the used turntable must also be able to slide back and forth.
(3) Changing the camber angle can change the camber angle at the same time, and changing the camber angle will cause the camber angle to change. Different suspension structures have different camber adjustment methods. If you move the upper bracket point or move the lower bracket point to the left or right, not only the camber angle changes, but also the inward tilt angle changes. Therefore, even if the camber angle is adjusted, the car is not smooth due to the change in the camber angle. Solved a problem and created another problem.
(4) The change of the toe angle of the rear wheel will affect the toe angle of the front wheel. The toe angle of the rear wheel will determine the angle of the rear wheel. Modern four-wheel positioning uses the propulsion line positioning method to determine the front wheel toe. Therefore, the front wheel toe angle is changed to cause the propulsion line to change. Although the toe beam does not change, since the reference line (propulsion line) of the single-wheel toe is changed, the single-wheel toe will also change, and the front wheel will be changed. Did not change because of this.