How can we make the cornering performance of the car stronger?

Drive at high speed in the car! The front wheels will tilt. The importance of four-wheel alignment can be illustrated by the knowledge of automobile four-wheel alignment. The four-wheel alignment angle is the relative angle between the suspension system and the moving parts. Keeping the correct four-wheel alignment angle can ensure the linearity and maneuverability of the vehicle, improve the steering performance of the vehicle, ensure the recovery of the steering system, and avoid the bearing from being damaged and losing accuracy due to improper stress. It can also ensure the close connection between the tire and the ground, reduce improper tire wear and gnawing, and ensure the stability when turning. The significance of four-wheel alignment The main positioning angles of automobile suspension system include camber, caster, toe-in, camber (K.P.I), toe-in when turning, etc. Its meaning is as follows: 1. Camber: defined as the angle formed by the tire centerline and the vertical line when viewed from the front of the vehicle, which is positive outward and negative inward. Different angles can change the contact point and stress point between the tire and the ground, which directly affects the grip and wear of the tire. The stress distribution of the vehicle weight on the axle is changed to avoid abnormal wear of the bearing. In addition, the existence of camber can be used to offset the angle change caused by the deformation of suspension system parts and the gap between movable surfaces after the car body is loaded. The existence of camber will also affect the direction of the car, just as a motorcycle can turn by tilting the body, so the camber of the left and right wheels must be equal, which will not affect the straightness of the car under the balance of force, and then cooperate with the toe-in to improve the straightness stability and avoid uneven tire consumption. Increasing negative camber needs to be combined with increasing toe; ; In order to increase positive camber, it is necessary to increase toe-in. 2. Angle of inclination (K.P.I): defined as the angle formed by the center line of the steering shaft and the vertical line. With the inclination angle, the weight of the vehicle can be evenly distributed on the bearing, which can protect the bearing from damage, make the steering force uniform and turn easily. On the other hand, if the camber angle is 0, the reaction force of the vehicle weight and the ground will produce great transverse shear stress on the axle, which will easily damage the axle and make the steering extremely heavy. In addition, camber angle is also the source of righting force after front wheel steering. Camber has been set at the beginning of vehicle suspension design and is usually not adjustable. 3. Toe: It is defined as the angle formed by the left and right tires when viewed from above, with toe inward and toe outward. The function of toe angle is to compensate the tendency of the tire to roll inward or outward due to camber and road resistance, and to ensure the straightness of the automobile. Toe-in will lead to understeer, while toe-in will increase the tendency of oversteer. 4. The caster angle of the kingpin is defined as the angle between the center line of the steering shaft and the vertical line when viewed from one side of the vehicle, which is negative forward and positive backward. The existence of caster angle of kingpin can make the intersection of steering shaft and road surface in front of the contact point of tire, and the resistance of road surface to tire can be used to keep the car running straight. Its principle is just like the front wheel of a shopping cart will automatically turn to the direction of your force and keep it straight. The greater the caster angle of the kingpin, the better the straightness of the car and the better the recovery of the steering wheel after steering, but it will make the steering heavy. The caster angle of an ordinary car is about 1~2 degrees. 5. Toe-in during steering: defined as the difference between the steering angles of the two front wheels during steering. When turning, the angle of the inner wheel is usually larger than that of the outer wheel, with a difference of about 2 degrees. Its purpose is to make the car turn smoothly around the instantaneous center of the extension line of the rear axle when turning. In addition, when the turning angle of the inner wheel is large, the resistance is also large, and the resistance difference can make the car lean to the side with large resistance, making it easy to turn (imagine the turning mode of the tanker). Offset Offset is defined as the distance between the rim mounting surface and the rim center, with positive offset toward the outside and negative offset toward the inside of the rim. Changing the offset of the rim will change the wheel track of the car, which refers to the distance between the tire center lines. Therefore, if the wheel rim and tire are simply enlarged without changing the offset, the wheel track will not be affected. If the influence of variable offset is replaced by a rim with a smaller positive offset, the wheel track will be widened, which can reduce the deviation of the center of gravity of the car body during cornering and improve the cornering speed limit of the car. However, the distance between the center of the steering shaft and the center of the tire is relatively increased, which leads to steering difficulties, increases the load of the steering mechanism and increases the deformation of the steering linkage mechanism, so it is necessary to appropriately increase the toe-in to correct it. But these are abnormal ways, so the front wheel offset should be as close as possible to the original offset value. For the rear wheel, when using a larger rim, if the bias is not changed, the inner side of the tire will often encounter the problem of suspension mechanism, so it is beneficial to use a rim with a smaller positive bias value without polishing the wheel arch. However, it should be noted that for cars with independent suspension of rear wheels, such changes will increase the change of rear wheel toe-in when accelerating and braking, which has no effect on ordinary street cars, but it is a big problem for racing cars. Let's take BMW's Series 5 (E34) as an example to see how the offset should change when the rim is enlarged. Initially, the iron ring provided by the original factory was 15*7J with an offset of 47, and the aluminum ring was 15*6J with an offset of 36; . When using 17 inch aluminum ring, the original factory provides 17*7.5J and offset 35, while Racing-Dydamic provides 17*8.5J and offset for the front wheel and 17*9J and offset for the rear wheel. Changing the offset will also affect the bearing load. Generally, the design of vehicle offset is aimed at the lowest bearing load when going straight. Although using a rim with a small positive offset will slightly increase the load when going straight (you don't have to worry too much about the load when the offset changes within 50mm), it can reduce the load when cornering. How to choose a four-wheel alignment shop with the evolution of suspension system from the most basic McPherson, trailing arm and double A-arm to three-joint, four-joint, five-joint and compound joint; The more connections, the more complicated the structure, and the higher the requirements for four-wheel positioning angle. So there will be a four-wheel alignment instrument designated by a certain model. The four-wheel locator is not used to adjust or change the positioning angle, but only to measure the positioning angle for technical reference. Technicians will compare the angle measured by the instrument with the angle set by the original factory. If it exceeds the design allowable range, some parts will be adjusted or replaced to restore the original design angle. Therefore, when you choose a four-wheel positioning store, you must remember that the quality of positioning instruments is of course important, but the "person" who adjusts the positioning angle is more important. Experienced and skilled technicians and advanced instruments are the best choice. Common positioning problems: how to judge the abnormality of chassis and suspension in daily driving and how to judge its reasons, I think readers want to know most. Here I put forward several typical questions for your reference. Poor linearity: When driving left or right, or the direction is not skewed, but the steering wheel is not straight, which is usually a typical positioning problem, but uneven tire wear or different types of tires used on the left and right wheels will also affect the linearity of the car. The most annoying problem of poor linearity may be that the steering wheel sometimes faces the road and sometimes has a small angle deviation when going straight, so the steering wheel can't stand still. The most likely reason is that the caster angle of the left and right wheels is deviated, resulting in different restoring forces of the left and right wheels, which is naturally susceptible to the influence of the road surface when the two forces are unbalanced. Steering wheel jitter: Steering wheel jitter is mostly caused by tire and rim problems, except for transmission shaft wear (FF car). Too high tire pressure or rim deformation will cause vehicle jitter, and poor tire roundness and inaccurate balance are the main reasons for steering wheel jitter. In addition, the uneven brake disc causes the jitter when braking, and the uneven braking force of the left and right wheels causes the deflection of the driving direction when braking, which are not solved by four-wheel positioning for you. Four-wheel alignment q &；; How often do I need to do the first and fourth rounds of positioning? Check the chassis and positioning at least once every six months according to the usage. If any angle exceeds the allowable value of the benchmark, some parts should be adjusted or replaced to make them return to the correct angle. Second, what are the common positioning problems? The most common positioning problems are the error of camber and toe angle caused by constant time vibration, and the change of caster angle caused by convex roads and holes. Third, how to detect the abnormality of the positioning angle? Generally speaking, about 60% of car owners who seek help because of abnormal positioning are due to poor straight-line driving performance, steering wheel angle leaning to one side, followed by steering wheel jitter, and uneven tire wear after driving for a period of time. Fourth, increase the rim size (inch). Should the positioning angle be modified when the offset changes? When increasing the rim size, try to use the same offset as the original rim size to ensure that the chassis can maintain its original performance. At present, the products on the market are limited by the product form and aesthetic considerations provided by the rim manufacturer, so when you change the rim, the other party will suggest that you change the rim with a smaller positive offset value, as long as the difference is not big and the wheel arch will not be worn, just slightly increase the toe-in. 5. When the short spring is used to lower the car body, will it change the positioning angle and how to correct it? When the short spring is used, the car body is lowered. For suspension system parts, its geometric change is just like the change of body lowering after the body is loaded. Therefore, unless the reduction amount is large, if the spring for the car body is reduced by 3~4 cm, there is no need to correct the positioning angle.