[100 Questions]Questions and answers on four-wheel alignment, the key to success or failure of chassis modification (Part 1)

The use environment of four-wheel alignment is not only in the modified car, but also in the original car, in order to have a stable dynamic response of the vehicle through the correct chassis positioning process, so as to obtain safe high-speed driving performance. Incorrect positioning settings are not only related to the tire wear speed, but also easily make people and vehicles in an unstable driving environment. The importance is even higher than other auto parts. It is a very important and basic automobile principle.

Question 1: Why do cars need four-wheel alignment? Let the tires roll at the correct angle.

Most car owners have heard the term "four-wheel alignment", and they all know that after replacing new tires or shock absorbers, they still need to go through this procedure to make the vehicle run normally, but why do the four tires need to be positioned, and how Which angles, or what problems will there be if they are not positioned, etc., I believe that there are not many car owners who really understand. In this way, the author will first introduce which chassis angles need to be positioned, but before the introduction, the author must first explain Yes, this unit does not intend to discuss the complex chassis positioning technology, but hopes to let everyone understand what the value displayed on the positioning machine is, and analyze whether the positioning of the car appears through the wear of the tires. Abnormal and other practical information, so it is very suitable for beginners.

Why do cars need four-wheel alignment? Simply put, it is for several purposes, namely vehicle straightness, average tire wear, tire cornering grip and high-speed driving stability. Since the four-wheel suspension of the vehicle is responsible for steering, shock absorption, straight running and rolling, etc., the front and rear wheel suspensions of the car are often equipped with many joints, which are composed of connecting rods and bearings, so that the tires can swing up and down or turn left and right. The range of motion, so that the car will be comfortable to sit up and turn when turning. Also because the four tires are not firmly fixed on the body, it is necessary to use the assistance of the instrument to confirm whether the rolling angle of the four wheels is normal, and also to check whether the bearings are worn or not. Let the tires run at different angles, not all of them roll forward, some roll to the right, some roll to the left, some roll sideways, and even if the tread eats one side, the vehicle will be very unstable at high speed. , and the tire wear rate will become faster, and the vehicle will have problems such as fuel consumption and tire deformation. Therefore, it takes a period of time for the car to perform four-wheel alignment. It is recommended to do it once a year.

Question 2: What is Camber-camber? From the front of the car, check whether the tires are inside or out.

In the four-wheel alignment, the common angles that generally need to be adjusted are: Camber, Toe-in/Out, and KPA, etc., which are described in detail as follows: First, the camber part , which is defined as the angle formed by the center line of the tire and the ground. Generally, the "outside eight" is this angle. If the upper end of the tire protrudes from the center vertical line of the tire, the camber angle is a "positive" value. When the upper end is submerged in the center line, the value is "negative"; in addition, when viewed from the front of the car, the length of the lower edge of the tire is greater than the upper edge, which means that the setting of the camber angle is negative, and vice versa, it represents a positive camber angle. If the negative camber is set to look like the vehicle is lying on the ground, the larger the angle, the more obvious it will be. At this time, it will increase the ground contact area of ​​the outer wheel when cornering, but it is not conducive to the straight-line driving and braking effect.

Generally speaking, on the independent suspension system, the camber angle plays the role of adjusting the contact surface between the tire and the ground. When the load is large, the camber angle tends to be negative. Therefore, when the four-wheel alignment is performed, the camber angle in the empty state is usually adjusted. Set in a positive direction, so you can get the correct camber when carrying passengers or items. However, in the arena, in order to allow the tires on the outside of the curve to obtain the largest ground contact area when the vehicle is cornering, the camber angle is usually set to a negative value, especially in the track with many sharp turns, the setting value of the camber angle is often As high as -3.5~-4.5 degrees, but too large camber angle setting, it is easy to cause the tire contact area to become smaller in the straight road section, but it is not conducive to the performance of grip and braking performance. How to master the correct positioning angle depends on long-term testing The combination of experience accumulation and driver's driving habits.

In addition, when performing Low-down in general, the camber angle will naturally increase towards a negative value, that is, the whole car will look like it is lying on the ground. If the K8 car series is concerned, the original camber angle of the front wheel is 0°±45', and the rear wheel is -1°±45'. Usually, if the camber angle is reduced by 30mm as an example, the camber angle of the front axle will be close to -1.30°~-2.30°, and the rear axle is about -2.00°~-3.00°. No matter in the visual effect of the appearance or the suppression of the actual vehicle roll, a considerable improvement will be obtained, but at this time, it is necessary to pay Yes: the wear rate of the tires will be more severe, but it can also be adjusted from other angles to suppress this situation to a relatively slight range, and in the actual positioning operation, the adjustment method also depends on the design of the vehicle itself vary from one to another.

On the traditional MacPherson suspension, it is usually done by adjusting the fixing screw between the shock absorber and the horn. On some early vehicles (such as: Impreza WRX), the original factory has an adjustable eccentric screw. To operate, but it was cancelled due to cost factors in the later stage, so the positioning stores in the market usually carry out the method of increasing the aperture. As long as it is within a certain range, the owner does not need to worry about its strength.

[100 Questions]Questions and answers on four-wheel alignment, the key to success or failure of chassis modification (Part 2)