The impression is that as long as the car runs off, most drivers think that it is the four wheel positioning, in fact, it is not, the cause of deviation is many: tire pressure will run off, tread pattern wear and tear will run off the same, suspension system design problems or suspension of injury, deformation, displacement... There will be a deviation phenomenon, in short, there are many reasons for the deviation. Headache can not be cured by cold. In the same way, all deviating phenomena can never be solved by making four rounds of positioning or moving a balance. Generally speaking, problems mainly focus on tires and suspension. You can first check the rated tire pressure given by the factory, most of the household cars are set between 2.0bar and 2.5bar, and the pressure values of the front and rear wheels are different. If the tire pressure is different, it will inevitably lead to deviation. In order to better use the tire, the position of the tire should be changed every twenty thousand kilometers, because the wear of the driving wheel is always larger than the other wheels, and the different friction will directly cause the deviation. The correct replacement method is that the front and rear wheels are paired at the same time, can not cross the diagonal before and after the adjustment; if the new tire needs to be changed, the same brand, the same pattern of tires should be replaced, and the four tyres should be replaced at the same time. Another common reason may be the four wheel positioning is not allowed, the front wheel obliquity, the main pin angle is not correct, or the front beam angle is too small and so will also cause deviation. The way to avoid it is to have fewer teeth on the road and to reduce the speed when crossing the big hole. As long as it is normal driving, there is no need to do four wheel positioning in general for one or two years. But if there is a situation, we must go to the professional maintenance station for testing, some small detection points, although the charge is cheap, but the adjustment is not allowed, it will not take long after the recurrence. Under normal suspension, the probability of running deviation is very low because of the suspension system failure, because the vehicle before the factory has been strictly tested and adjusted by the manufacturer. But it does not exclude the original design problems, such as the suspension rod and steering linkage movement interference will affect the vehicle deviation. The former is caused by errors caused by manufacturing and adjustment, and the latter is caused by the original design, and the latter causes more deviation to the right. There are more reasons for the old car running off. In addition to the above conditions, the frame deformation, the front axle shift, the negative front beam and the vertical arm, the two front plate spring shrapnel are different, and the horizontal, straight rod and ball pins will cause the deviation, so the specific situation of the old car should be analyzed concretely. If the deviation phenomenon is aggravated during braking, we should focus on checking the brake system, because the braking force on the left and right sides of the wheel will also cause deviation. First of all, it is necessary to see whether there are oil pollution, water wet or hardening on the brake disc of the front wheel, and when the brake disc and the disc are normal, check the oil leakage, the loosening of the fixed support plate of the brake pincers, the friction plate has no back position and so on. Secondly, the quality of the steering system will also affect the straight line of the car. Because of the excessive wear gap or the loosening of the bearing, main pin and wear of the bushing, the joints will cause the car to swing the head and can not keep the normal track. If the steering knuckle arm and steering knuckle bend deformation, it will cause the vehicle to run away one way. The most serious problem is the loosening of the ball after the serious wear of the straight rod, which will cause the steering failure, and the car will be completely out of control. It is suggested that the slight deviation will result in the failure of the tire and tyre, and the occurrence of dangerous conditions such as tire bursts and vehicle out of control. According to the survey, for ordinary family cars, the probability of birth after 150 kilometers per hour is less than 20%; running deviation is not the kind of fault that can let the car break down, but there are many hidden dangers in the long run of the vehicle, so it is advised that the owner of the car should be "sick and early doctor" again.