When do you need to do four-wheel alignment?

1.The driving performance of the vehicle has been affected(the driver feels that the most direct thing is the deviation,which is also counted as one if the steering wheel does not return automatically)

2.Damage to chassis and suspension caused by accident

3.Abnormal tire wear(but it should also be considered whether the abnormal wear is caused by abnormal tire pressure.Generally,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 one side is eccentric wear,it may be caused by deviation of camber angle;abnormal wear caused by toe-in will be mentioned below)

4.The axle and suspension parts have been removed

Why do you need to adjust the four-wheel alignment?I'm sure you can tell the reason.The vehicle is running sideways.Everyone knows that you need to adjust the four-wheel alignment,because it affects your driving experience.Does it mean there is no problem if you don't run sideways?Whether the answer is yes or no,it is somewhat one-sided.If the chassis data changes quietly,it will certainly change the driving characteristics,but the deviation is a phenomenon that can be perceived by most people.

For those hidden changes,you need to be more careful to detect them,but it seems that most people do not have the ability to do so.The wear of tyres can reflect some subtle changes more realistically.For example,the uneven wear of the inner and outer sides of a single tyre may be caused by abnormal changes in the camber value(of course,daily driving habits should also be considered),However,if the tread has regular undulation(sawtooth wear),which is likely to be accompanied by abnormal tire noise,it can be considered that the toe-in has a relatively serious deviation and needs to be repaired at the tire shop as soon as possible.Whether the tire needs to be replaced depends on the wear condition.If the tire is too worn,the data made by four-wheel alignment will also be inaccurate,We will talk about the inspection of the front tire after positioning.

As a normal wear and tear component,the repair of the suspension part is unavoidable.The abnormal noise caused by the aging of the buffer rubber sleeve is relatively common.After replacing the relevant components,in principle,it is also necessary to do four-wheel alignment.Such a statement may cause opposition from all sides.Indeed,this is not in line with the concept of most people.Few people clamour to do four-wheel alignment because of replacing the suspension parts,This approach will not be understood.Why do I need to do positioning when I change a control arm?The reason is that the relative installation position will change when we disassemble the suspension.That is,the incalculable installation error may lead to abnormal positioning data.In order to kill everything,positioning is necessary in principle.However,in the process of installation,the maintenance technician will basically fasten the screws on the original marks(marks will be left when the screws are removed)to minimize the changes in positioning data caused by disassembly and assembly.

It is worth mentioning that the new car is not suitable for four-wheel positioning,because the chassis has a settling process,just like the engine needs to be running-in.The"running-in period"of the chassis is about 2000 km.

Inspection before four-wheel alignment

1.Tyre(tread depth and tyre pressure)

The data of four-wheel alignment is formed under a relatively standard condition,so the original calibration conditions should also be followed when calibrating the four-wheel alignment.In order to ensure that the front and rear axles are on the same horizontal plane,we should pay attention to the tyres.First,the dimensions of the four wheels should be the same;In addition,minor differences should also be taken into account,for example,the tire pressure should be adjusted in place according to the standard(see the inner side of the fuel tank cap for the tire pressure standard);There is also a more detailed inspection.The tread depth needs to be measured.The maximum deviation of the tread depth on the coaxial line cannot exceed 2mm.If the conditions are not met,the relevant tires need to be replaced as appropriate.

The new generation of four-wheel positioning system will be more intelligent.By inputting these measured data into the system,the maintenance technician can calculate according to the corresponding values to compensate for the errors caused by these external factors.

2.Suspension(visual inspection of suspension status)

The good condition of the wheels does not mean the beginning of a perfect four-wheel alignment adjustment.You should also ensure that the chassis is also in a healthy condition.This is more about the accident of the car.Sometimes,the chassis will inevitably be damaged to a certain extent after the car is hit,and even deformed and broken.The replaced chassis components will not have too many problems,On the contrary,it is those parts that do not show any sign on the surface that are most likely to lead to the deviation of the four-wheel alignment.Therefore,Master Chen,who led me to complete this task,always put the sentence"nothing that can be seen is a fault"on the lips.

3.Conditions to be met under no-load condition(keep the no-load condition as it should be)

This is the most easily overlooked link.It is the same everywhere.It seems that no one pays attention to it.The vehicle parked on the lift should be in an empty state,and the spare wheel and the vehicle tools should be placed in their respective positions,which is easy to understand and achieve.The harsh requirement is that the oil storage capacity of the tank and the liquid storage capacity in the glass kettle are also advertised,which need to reach more than 90%.Why do you want to ask?I can only tell you that the manufacturer set it under this condition,but you want to ask me why the fuel tank is always empty when you buy the car.Is it pumped out after the adjustment?I really can't answer that.Maybe it can also complete the numerical compensation for the new generation of four-wheel positioning system.

Parking of vehicles

It is not easy to do a four-wheel alignment.It seems to me that it is not easy to drive the car onto the lift and park it in the correct position.First,not only should the car body be upright,but also the front and rear wheels should be in the center of the electronic steering wheel and the rear sliding plate.

Fixture and target disk installation

The fixture is equivalent to the adapter that the target disk is fixed on the wheel.It is used to fix the wheel.In order to cope with the size of different rims,the fixture fixing arm can be adjusted accordingly.The fixture has three fixed arms in total,and each fixed arm end has a claw to hold the rim edge to ensure a plane is determined at three points.However,in the actual operation process,I found that no matter how adjusted,there will always be a claw that can not adhere to the rim edge as honestly as the other two,which can not become a plane.(Please remember this picture.It is very important.We will talk about how to solve this error later.).

Selection of vehicle type information

Not only that,I also need to find the corresponding vehicle model in the system to retrieve the relevant data information,which is the basis for measuring whether the chassis data of this vehicle is correct.Therefore,the selection of vehicle model cannot be wrong.This is especially important when positioning in Auto Parts City.In order to deal with door-to-door business,their system stores a large number of chassis information of different brands and models.After finding the corresponding model year,the effect will be posted.

The most neglected"cart compensation"

Do you remember the scene just now?My question about determining a plane at three points is to be solved.This procedure is called"offset compensation"in the system.So far,this is the time for big action.It also shows me how powerful this lift is.

Test before adjustment

After such a long time,so much work has been done,and the following inspection before adjustment is really a response to the sentence"three points to seven points to prepare".In essence,it is still the preparation work,or to determine the status of the wheels more accurately.