The four-wheel positioning is not for the wheel itself, it is for the length and position of various tie rods. A wheel is not randomly installed on the car, it is at an Angle. Like overpitch, the wheel is not perpendicular to the ground, it tilts outward. Another example is the front beam, after hitting the positive direction, the wheel is not pointing to the front, it is tilted inward, two wheels formed an inner eight. The formation of this position of the wheel is determined by the position of the suspension of various tie rods. The adjustment of the positioning value is to adjust the position of the rod or suspension and other components. Generally speaking, four-wheel positioning is to ensure that the tire and the ground are closely combined by adjusting the geometric Angle of the tire and steering, suspension and other components. Because the installation between the four wheels of the vehicle, the steering mechanism and the front and rear axles should have a certain relative position, the relative position is the standard value formulated by the manufacturer. Adjust and restore the installation of this position, that is, four-wheel positioning.
Four-wheel positioning can make the car keep stable straight driving and light steering, and reduce the tire and steering parts wear.
Four wheel positioning includes six contents: kingpin rear-tilt (Angle), kingpin rear-tilt (Angle), front wheel overtilt (Angle), rear wheel overtilt (Angle), front wheel front bundle and rear wheel front bundle. It should be noted that four-wheel positioning is to adjust the Angle coefficient between the vehicle chassis system. It is a means of maintenance and should not be done easily.
When do I need to do four-wheel positioning
(1), the vehicle driving performance is affected (such as the vehicle deviation, steering accuracy becomes worse, "gnawing tire" serious, playing the direction can not automatically back wheel phenomenon).
(2) Damage to chassis and suspension caused by accidents.
(3) Abnormal tire wear. (It is also necessary to consider whether the abnormal wear is caused by abnormal tire pressure. In general, high tire pressure will aggravate the wear in the center of the tread, while low tire pressure will aggravate the wear on both sides of the tread; If there is wear on one side, the camber may be off.)
(4) Parts of axle and suspension have been removed. (Many modified car enthusiasts like to replace the original shock absorber, after replacement must also do four wheel positioning.)
Why does the positioning imbalance occur
I just said, how can it be wrong to use it? How can it be wrong to use it?
Car bumps, accidents, parts wear, replace a new, will make the wheel Angle changes.
It is easy to understand, for example, doesn't the suspension bounce around? Not every wheel is subjected to the same force.
Our road is oblique, some have pits on the ground, some do not have pits, you accidentally press a curb, right press up, left on the ground temporarily stop, it is possible.
For a long time, the force of the wheel, bending Angle is a little larger; The force of the wheel is small, its deformation is small, in general, is not coordinated, inconsistent.
What is dynamic balance
Dynamic balance is the weight deviation between the tire and the underwire, which is manifested in that the steering wheel will shake after the car starts, and it is generally a speed segment, such as between 60 and 80, less than 60 will not, higher than 80 will not.
Dynamic balance is for the wheel, the tire is mounted on the hub, the tire and hub manufacturing accuracy will always have errors, resulting in the weight of each point on the wheel can not be exactly the same. A wheel is heavy in some places and light in some places, so it will spin up the phenomenon of shaking. Just like a fan, if all wings are the same, it can rotate smoothly without shaking. If one wing is changed into a different one, lighter or heavier than the other wings, it will cause unstable rotation of the fan and serious shaking. The same is true of tire rotation, a point is lighter or heavier than the same place on the opposite side, it will spin unstable.
Dynamic equilibrium is the solution to uneven mass distribution. How was it solved? By adding a counterweight, if a point is 10 grams lighter than the same point on the other side, then add 10 grams of counterweight to that point, and you get the same weight. Dynamic balancing is basically looking for light points on the wheel and adding a counterweight to them. The wheel has a slight imbalance, driving generally can not feel abnormal, the gap is below 10 grams, generally can not feel, above 10 grams, high speed will feel obvious jitter.
When the wheel rotates at a high speed, it will form a dynamic unbalanced state, causing the vehicle in the driving wheel jitter, steering wheel vibration phenomenon. In order to avoid or eliminate this phenomenon, it is necessary to make the wheel adjust the balance of each edge part by increasing the counterweight method under the dynamic condition. This correction process is called dynamic balancing.
Dynamic balance can ensure that the tire can run smoothly, avoid shaking, so that the vehicle is more stable and safe at high speed.
What happens when you need to do dynamic balancing
(1) Replace or repair the tire system (tire or hub).
(2), routine maintenance, remove the tire inspection, should do dynamic balance detection. (Some vehicles because of too long use time, will cause the "dynamic balance weight block" off, resulting in tire balance imbalance, so it is necessary to detect dynamic balance.)
(3) High-speed driving, body, steering wheel shaking phenomenon.
Simply put, four-wheel positioning is the inspection and correction of the vehicle running track, including the adjustment of suspension, chassis, parts and so on.
The dynamic balance merely equalizes the distribution of the wheel's mass a little, making it spin round.
Therefore, in the case of common car deviation, the first thing to check is whether the four-wheel positioning is accurate, rather than looking at dynamic balance.
Now that you know what dynamic balancing and four-wheel positioning are, how often do they do it? It can simply be said that if there is a problem, do it; if there is no problem, do not need to do it; there is no fixed number of miles. The performance of the wheel imbalance is the high-speed steering wheel shake, positioning is not correct performance is deviated, eat tire, steering wheel is not correct, the direction of automatic return. With the wear of tires, some potholes do not slow down resulting in a slight deformation of the wheel hub, etc., the wheel will become unbalanced, so sometimes the tire repair factory will suggest that the dynamic balance is done together, in order to prevent the phenomenon of tire shaking.
All removed and installed tires, is to remove the tires from the hub, must do balance, such as tire repair, replacement of new tires, etc. The frequency of dynamic balance is relatively high. As for four-wheel positioning, it is best not to do it easily. Sometimes, the equipment fineness and personnel technical problems may be no problem. The car has a fault to do, no fault do not as a maintenance project regularly.