1 Ensure the correct tire pressure.
The air pressure standards of front and rear wheels and spare tires of different vehicles are also different. Standard tire pressure data provided by automobile manufacturers are generally pasted on vehicle doorposts and other parts. If the air pressure increases by 25%, the tire life will be shortened by about 30%.
2 Tire appearance inspection
Always check the tires for bumps, cracks, cuts, nails and abnormal wear. Pay special attention to the inspection of tire tread and tire edge wear, which is often caused by poor positioning or abnormal tire pressure.
3 Keep the tire surface clean.
Keeping clean is one of the important factors to prolong tire life. Especially before and after driving in winter, we should pay attention to the cleanliness of tires and check whether the tire patterns are covered with snow and ice before driving. Especially when the tire tread is hard, don't pry it forcibly, and don't pour boiling water on the tire. Water the tires with normal temperature water and clean them up. At the same time, it is also necessary to check whether there are stones, iron blocks, nails and other foreign bodies in the pattern, especially new tires, and clean them up in time.
4 Positioning and balance of tires
If uneven tire wear or excessive vehicle vibration is found, it may be caused by poor positioning or imbalance. These conditions will not only shorten the service life of tires, but also affect the handling performance of vehicles. You should go to the maintenance station for inspection immediately, and carry out four-wheel alignment or tire dynamic balance according to the inspection results.
2. How much do you know about four-wheel alignment?
First, the king pin inclination:
In addition, the inclination angle of the kingpin also reduces the distance from the intersection point between the kingpin axis and the road surface to the intersection point between the wheel center plane and the ground, thus reducing the force exerted by the driver on the steering wheel during steering, making the steering operation lighter and reducing the impact force transmitted from the steering wheel to the steering wheel. However, the inclination angle of the kingpin should not be too large, otherwise the tire wear will be accelerated.
Second, the caster angle:
Looking at the wheel from the side, the steering kingpin (the center of rotation of the wheel when turning) leans backward, which is called kingpin caster. After the caster angle of the kingpin is set, the distance between the center line grounding point of the kingpin and the ground projection point of the wheel center (called kingpin pitch, which is the same as the principle that the front wheel fork beam of the bicycle leans backwards) is generated, so that the wheel grounding point is located at the back end of the extension line of the steering kingpin, and the wheel is pulled backwards through rolling resistance during driving, so that the wheel direction naturally faces the driving direction.
Setting a large caster angle of the kingpin can improve the straight running performance, and at the same time, the pitch of the kingpin also increases. Excessive pitch of the kingpin will make the steering wheel heavy, and the front and rear bumps of the wheels will be aggravated by road interference.
Third, the front wheel camber:
When looking at the wheel from the front and rear direction, the tire is not installed vertically, but slightly inclined in the shape of Zhang Kaicheng, which is called negative camber, and the one that opens in the opposite direction is called positive camber. In the heyday when diagonal tires were used, the camber angle was set to be relatively large because the tires touched the ground obliquely, which was convenient for the operation of the steering wheel. Nowadays, cars generally set the camber angle very small, close to vertical. Flat radial tires for automobiles are becoming more and more popular. Due to the characteristics of radial tire (high tread rigidity and wide tread), if camber is set, the tire will be eccentric and the tire friction will be reduced. Due to the continuous use of power steering mechanism, camber angle is also shrinking. However, setting a small camber angle can exert appropriate lateral thrust on the wheel bearings on the axle.
Fourth, the front toe:
The toes are inward, and the so-called inner splayed feet mean that the left and right front wheels are inward respectively. The purpose of adopting this structure is to correct the outward rotation of the wheel caused by the camber angle of the front wheel. As mentioned earlier, steering wheel operation becomes easy due to camber angle. On the other hand, due to the inclination of the wheels, the left and right front wheels rotate outward respectively. In order to correct this problem, if the left and right wheels have inward angles, plus or MINUS zero, the left and right wheels can keep moving in a straight line and reduce tire wear.
The role of four-wheel alignment:
When users use the vehicle for a long time, they find that the steering is heavy, swaying, running off, incorrect, and not righting, or abnormal wear such as unilateral wear, wavy wear, block wear, and eccentric wear of tires, and the car feels drifting, bouncing, shaking, etc. when users drive. They should consider checking the wheel alignment value to see if there is too much deviation and repair it in time.
(1) Front wheel alignment includes caster, caster, camber and toe-in.
(2) Rear wheel positioning includes rear wheel camber and toe-in one by one. Such front wheel positioning and rear wheel positioning are generally called wheel positioning, which is often called four-wheel positioning. The function of wheel alignment is to keep the car running smoothly in a straight line and steering lightly, and reduce the wear of tires and steering parts when the car is running.
Let me explain here that the above four positioning values are all indicators of front wheel positioning. The rear wheel alignment value is similar to the front wheel alignment value, but the rear wheel alignment of most cars is not adjustable.
Answer: If the data suggested in your vehicle manual is the same as that in the four-wheel locator computer, it is universal. Generally speaking, the following situations require four-wheel alignment.
1, after replacing a new tire or repairing a collision accident;
2. Unilateral eccentric wear of front and rear tires;
3. The steering wheel is too heavy or floats and shakes when driving;
4. When going straight, the car deviates to the left or right;
Although there is no such situation, for the purpose of maintenance, it is suggested that the new car should be driven for three months, once every six months or ten thousand kilometers.
Four-wheel alignment is one of the necessary work contents of automobile maintenance. Unless there are obvious related problems before four-wheel alignment, such as poor linear stability, you can feel it immediately after four-wheel alignment, otherwise it is difficult to judge whether it is good or not by feeling. At present, the quality of the auto repair industry is uneven. I suggest you try to go to a better maintenance company to ensure the quality of four-wheel alignment and traffic safety. Its advantages are:
1. Enhance driving comfort;
2. Reduce gasoline consumption;
3. Increase the service life of tires
4. Ensure the linear stability of the vehicle;
5. Reduce the wear of chassis suspension fittings; 6. Improve driving safety
3. What is the four-round review memory method?
Hello, four rounds of review:
The first round: read the data (materials) comprehensively, check for leaks and fill gaps, and sort out and summarize all kinds of knowledge on this basis to make it systematic. The second round: focus on solving the key and difficult points in the textbook and personal learning difficulties. The third round: pay attention to problem-solving training. In addition to doing some simulated test questions to warm up before the exam, we should also conduct individual training for our weak links in the test questions. The fourth round: Pay attention to the memory of knowledge in order to keep "fresh in memory" in the exam. The time can be adjusted according to your own potential, and the fourth round 15 days should be strictly guaranteed as far as possible.
The four-round review method pays attention to efficiency, so I will give you some methods and ideas to improve the review efficiency according to my own experience.
First of all, you should learn to plan your own time, what to do in each time period, and be clear according to your own learning situation. Only with the goal learning can we have a direction, and then we can calm down and concentrate on it, complete it in an orderly way, and improve efficiency and performance.
Second, improve efficiency. I practice "fast reading" to stimulate the potential of the right brain and improve the efficiency of study and review. Speed reading is an effective method of learning and reviewing. Its training principle lies in activating our "brain-eye" potential, cultivating us to directly convert text symbols perceived by visual organs into meanings, eliminating potential pronunciation phenomena in our minds, spanning the process from pronunciation to understanding meanings, forming a reading mode directly reflected by eyes and brains, and realizing a leap in reading speed, overall perception, understanding and memory, and concentration.
Specific exercises can refer to: Jingying Special Speed Reading Memory Training Network, and you can try training by installing the software. Practice with software for more than 1 hour every day for one month, which can improve your reading speed by 5- 10 times, and improve your memory and comprehension accordingly, and finally improve the efficiency of study and review and achieve good results. At present, many classes in our school carry out holiday speed reading shorthand training courses, using the elite speed reading memory training system.
Besides, doing exercises is the best way to check your study and review. Be selective when doing the questions, not aimless. At the same time, we should pay attention to doing problems, and it is best to sort out an error-prone exercise book. You can do one or two sets of simulation questions in the early stage of the exam, and you should limit the time and take the exam according to the standard, so as to cultivate the test mentality. For more specific learning and review methods, you can post "Efficient Learning Method" to check the exchange.
4. What is the four-wheel drive in automobile common sense?
Four-wheel drive is the basic configuration of off-road vehicles and urban multi-function vehicles.
There are generally two kinds of four-wheel drive: constant four-wheel drive and semi-four-wheel drive. Semi-four-wheel drive vehicles usually use two-wheel drive, and only use four-wheel drive when necessary.
A four-wheel drive vehicle is always in a four-wheel drive state. Structurally, four-wheel drive usually has one more central differential than semi-four-wheel drive, thus avoiding the phenomenon of sharp turning braking.
Four-wheel drive vehicles, especially ordinary four-wheel drive vehicles, have excellent driving performance, and the specific advantages are as follows. 1, improving passability: Because all four wheels of a four-wheel drive vehicle transmit power, the vehicle obtains twice the driving force as that of a two-wheel drive vehicle.
The front and rear wheels support each other, which greatly improves the trafficability of wet, snowy and uneven roads. 2. Improve climbing ability: Similarly, four-wheel drive vehicles can climb steep slopes that two-wheel drive vehicles cannot climb.
3. Excellent cornering performance: the adhesion of tires is closely related to the power transmitted to the road surface. With the increase of power, the cornering force of tire tends to decrease. The power is reduced, the steering force is increased, and the performance of wet road surface and lane change is improved.
4. Excellent starting and accelerating performance: In a four-wheel drive vehicle, the engine power is transmitted to all four wheels evenly, and the adhesion of all four wheels can be effectively utilized. Therefore, even if the accelerator pedal is suddenly stepped to the bottom, the wheels will not idle, thus improving the starting and acceleration performance of the vehicle.
5. Stability of straight driving: With the increase of the residual adhesion of each wheel, the ability of the wheel to resist external disturbance is enhanced. Therefore, the constant four-wheel drive shows superior directional stability.
5. What is the common sense of tire maintenance?
Does the landlord want to solve the problem by himself? It's good.
Start with low temperature. The cold in winter makes tires brittle and elastic. When driving again after parking for a long time or staying overnight, you should slowly lift the clutch pedal when starting, start smoothly, drive at a low speed first, and then drive normally after the tire temperature rises.
After stopping on the ice for a period of time, the grounding part may freeze, so be extra careful when starting to prevent the tread from being torn. When parking in the open air for a long time in winter, you should put wood or sand under the tires.
6. Tire temperature, tire friction and deformation will generate heat, which will increase the temperature and air pressure inside the tire. When the tire temperature is very high, you can't deflate and depressurize it, let alone pour water on the tire to cool it down. Instead, you should rest in a cool and ventilated place until the tire temperature drops.
If you stop halfway, you should develop the habit of safe parking, choose flat, clean and oil-free ground parking, and pay more attention to the car beauty franchise store for valet.
6. Automobile tire knowledge
As one of the important parts of the vehicle, the tire is not only related to the handling performance of the vehicle, but also related to the life safety of the people on the vehicle. According to statistics, 46% of highway traffic accidents are caused by tire failure. In this issue, tire maintenance experts from American auto accessories and automobile department stores will answer questions for the majority of car owners on how to do tire inspection and maintenance well.
tyre pressure
The "health" of tires is inseparable from air pressure. Abnormal tire pressure will lead to local tire wear, reduced handling comfort, increased fuel consumption and other problems, and then lead to tire puncture. Therefore, it is the key to maintain the standard tire pressure and monitor the tire pressure change in real time.
First of all, the tire pressure gauge
Car owners know that the tire pressure should be kept within the standard pressure range required by the manufacturer, so they should always check the tire pressure. Secondly, when the vehicle is driving at a high speed, the rapid increase of tire temperature may still lead to abnormal tire pressure and bury hidden dangers. Real-time monitoring of tire pressure at high speed is also particularly important. "TPMS" is a real-time tire pressure detection system. Sensors are placed inside the steel ring, and the tire pressure and tire temperature are displayed on the LCD screen through wireless transmission. If there is any abnormality, it will automatically give an alarm.
Second, the tire is full of nitrogen.
The high temperature generated at high speed will lead to abnormal tire pressure. Removing the original air in the tire and filling it with dry nitrogen can keep the normal tire pressure for a long time. Because nitrogen is an inert gas, its expansion coefficient is low, and it is not easy to increase with the change of temperature, so the probability of puncture can be minimized. In addition, because nitrogen does not contain water, it can also delay the oxidation speed of the inner wall of the tire.
figure
The tread block of the tire is the only part of the vehicle that touches the ground. After long-term friction with the ground, the pattern gradually becomes shallow. It should be stopped when it is worn to replace the mark. However, due to the serious wear and tear of individual tires or tires, many vehicles have to be scrapped in advance.
One-wheel and four-wheel alignment
After driving for a period of time, there will be problems such as vehicle deviation, steering wheel sinking and unilateral tire wear, which are all caused by wheel alignment angle deviation. At this time, the vehicle should be tested for four-wheel alignment. If it exceeds the allowable range, it should be adjusted immediately.
Second, dynamic balance.
Replacing tires, wheels or wheels subjected to heavy impact will lead to uneven distribution of wheel mass, steering wheel will shake when driving, vehicle will bump and shake, and tire wear will increase. In order to eliminate this situation, it is necessary to dynamically balance the wheels. In addition, experts from American auto supplies and auto department stores remind car owners to try their best to correct bad driving habits such as sudden braking, sharp turning, sudden start and quick stop, so as to reduce tire wear and prolong tire service life.
wound
In addition to checking the tire pressure and tread pattern, the owner should also pay attention to whether there are the following problems on the tire surface:
1) Whether the tread is cracked. The tire rubber will harden and crack after aging, indicating that the tire has reached the replacement limit, the tire grip is reduced, and the cracked part is prone to rupture and puncture due to external impact during driving.
2) Whether the tread is cut or nailed. All these may cause tire leakage and eventually puncture, which will become a safety hazard if not found in time.
3) After the tire is hit, check whether the tread is bulging in time. If it bulges, it means that the sidewall ply has been broken, and there is a possibility of puncture at any time.
7. Automobile four-wheel positioning knowledge
The suspension system will wear out if it is used for a long time, and the external impact will also deform the suspension parts, which will lead to the deviation of the toe-in, wheel inclination and caster angle of the kingpin from the design angle, which will easily lead to tire biting, direction swing, poor handling performance and even potential safety hazards.
Therefore, the measurement principle of four-wheel positioning At present, there are four kinds of positioning instruments commonly used in four-wheel positioning, namely, cable-pulling, optical, computer cable-pulling and computer laser. Their measurement principle is the same, but the measurement method (or the type of sensor used) and the way of data recording transmission are different. This paper only introduces the measuring principles of several important testing items that can be measured by the four-wheel alignment instrument. 6. 1. 1. 1 Measuring principle of wheel toe-in and thrust angle. When getting off the toe-in, make sure that the car body is straight and the steering wheel is in the middle position. In order to improve the measurement accuracy of the toe-in value (or toe angle) of the wheel, whether it is a cable-type, optical or computer-based four-wheel aligner, before detecting the toe-in, it is often necessary to form a closed right-angled quadrilateral by means of cable or light irradiation or reflection.
When the vehicle to be inspected is placed in this quadrangle, not only the front toe-in and rear toe-in can be detected by optical mirrors or sensors installed on the wheels, but also the coaxiality of the left and right wheels (that is, the coaxiality of the left and right wheels on the same axle) and the thrust angle can be detected. Because the sensors used in the four-wheel alignment system are different, the measurement methods are also different. Here, the measurement principle of wheel toe-in is only explained by phototransistor sensor.
Fig. 6- 1 8 closed quadrilateral phototransistor composed of light beams is a near-infrared receiving tube and a photoelectric conversion device. Its structure and shape are shown in Figure 6-2. Its working state is: no voltage, using the principle of pn junction receiving light to generate DC voltage, used as a smiling photovoltaic cell.
Some signal receiving elements are connected behind the phototransistor, so that the signals obtained on the phototransistor can be analyzed and processed in time. Figure 6-2 Structure and shape of photodiode. Phototransistor sensors installed on two front wheels and two rear wheels have the function of receiving and emitting (or reflecting) light, and a quadrilateral similar to that shown in Figure 6-2 can be formed by transmitting and receiving between them.
Phototransistors are arranged in rows at equal distances on the light receiving surface of the sensor. When the phototransistor receives light irradiation at different positions, the electrical signal generated by the phototransistor represents the magnitude of toe angle or thrust angle. Specifically, when the current beam is zero, the beams emitted (or reflected) by the sensors on the left and right wheels on the same axis should coincide.
When it is detected that the two beams of light are parallel but not coincident, it means that the axes of the left and right wheels are different (that is, the automobile is misaligned). At this time, the wheelbase difference between the left and right wheels can be measured according to the information of the output deviation of the photosensitive tube. When the left and right wheels have toe-in, the beam position received on the left wheel sensor will have a deviation value (note the sign) from the original zero position, which means the toe-in value (or toe angle) of the right wheel. Similarly, the deviation of the beam position received by the right sensor from the original zero position indicates the toe-in value (or toe angle) of the left wheel.
The simple schematic diagram of its measuring principle is shown in Figure 6-3. 1- dial 2- projecting arm 3- phototransistor 4- laser disc 5- projecting laser beam 6- receiving laser beam 1~4- optical receiver 5- front wheel 6- rear wheel 7- longitudinal axis of automobile-thrust angle Figure 6-3 Measurement schematic diagram of wheel toe angle 6-4 Measurement principle of thrust angle based on the above detection principle, the front and rear axles of the inspected vehicle can be detected at the same time.
Similarly, through the sensor installed on the rear wheel, we can detect the size and direction of the toe-in value of the rear wheel (toe angle of the rear wheel). 6. 1. 1.2 Measuring principle of caster angle and caster angle. The measurement of camber, caster angle and caster angle are all about angle measurement. Except for the optical four-wheel alignment instrument, which does not use sensors to measure camber and toe-in, all other types of four-wheel alignment instruments use sensors to measure angles, including toe angle.
The caster angle and camber angle can not be measured directly, but only indirectly according to the geometric relationship. In order to understand the measurement principle, we might as well know it from the perceptual point of view first.
Take a socket wrench as an example. First, stand the wrench bar vertically on the desktop, so that the wrench bar is vertical to the line of sight and horizontal. This lever is the steering knuckle shaft (the left front axle when facing the front of the car). The lower end of the wrench bar deflects an angle in front of you, that is, the caster angle of the kingpin is formed, and then the position rotates inward and outward around the axis of the wrench handle respectively. At this time, you will find that the wrench connecting rod deflects upward and downward around the horizontal plane respectively (as shown in Figure 6-5).
Figure 6-5 Measuring principle of caster angle of kingpin The measuring principle of camber angle is cancelled as shown in Figure 6-6. Tie a long connecting rod to the wrench connecting rod head, and the long connecting rod is perpendicular to the wrench connecting rod. Stand the wrench upright on the table, keep the long extension rod in a horizontal position and perpendicular to the line of sight, then deflect the lower end of the wrench handle inward by an angle, that is, form an offset internal inclination angle (equivalent to looking from the outside of the left front wheel), and then rotate around the axis of the wrench handle from this position. At this time, it will be found that the extension rod rotates counterclockwise and clockwise respectively (as shown in Figure 6-6).
Figure 6-6 Measuring principle of kingpin inclination, geometric relationship between kingpin inclination and kingpin inclination, and various push analysis relationships, one of which is introduced below. (1) Measuring principle of caster angle: Take the left front wheel as an example. When the wheel rotates left and right = 20 (as shown in Figure -7), ZO is the kingpin axis, OB is the steering wheel axis, the quadrilateral DEFG represents the horizontal plane, and the included angle of quadrilateral HIJK with respect to the plane is the kingpin caster angle.
The LMNP plane is a plane perpendicular to the kingpin, which is composed of the HIJK plane with ST as the axis rotation angle (kingpin inclination angle), and OD is the direction of the steering knuckle axis plane when the wheel rotates 20 to the left. Line segments LD, A'b', AB, A' B', MI, FN and KP are all vertical lines on the horizontal plane DEFG.
Figure 6-7 Calculation diagram of kingpin caster angle measurement principle is obtained from Figure 6-7 Calculation diagram of kingpin caster angle measurement principle (derivation engineering is omitted): When the above formula indicates the specific angle, the kingpin angle is.
8. Seek knowledge of automobile tires
The following are common tire size representations: for example:185/70r 1486h185: tread width (mm) 70: flattening ratio (tire height ÷ tire width) r: radial structure14: rim diameter (inch
The letters A to Z represent the certified speed grades of tires, ranging from 4.8 km/h to 300 km/h ... Common speed grades are: Q160 km/HV240/HR170 km/HW270/H S180 km/HY300 km/.
For example, P275/40ZR 17 93W, the highest speed level ("W" in "93W") is 270km/h Q: Tips for tire use ① Ordinary automobile tires have no directionality, and in principle they can be interchanged left and right (unlike F 1 racing tires, which have strict directionality); ② Jetta suggests that the front and rear tires should be used interchangeably every 20,000KM (Fei Xian: I read the literature that the rear wheels can be moved to the front in parallel and the front wheels can be switched to the back.
The reason is that, generally speaking, the wear of automobile tires is greater in the front than in the back, because the front has steering function; The right side is bigger than the left side, because the road is curved, and the tire stroke on the right side will be longer. ); (3) The tire aging is not obvious, whether it is aging or wear, or mileage and road conditions account for most of the reasons; That is to say, the driving years should not be used as the criterion for judging whether to replace tires, but the driving mileage should be used as the main parameter, and the most important thing is the degree of tire wear (Fei Xian: unfortunately, there is no map now, which can clearly indicate which pattern must be replaced as soon as possible, please look it up in DX); (4) blindly increasing the hub is not good, and the braking effect will be worse.
Because the braking force of the braking mechanism may be insufficient; ⑤ Using too wide tires will enhance comfort and stability, but fuel consumption will increase and braking will be problematic; ⑥ Try to use and replace tires in pairs. By keeping a pair of tires in similar wear and working conditions, the left and right balance of the vehicle can be guaranteed (Fei Xian: When each tire is replaced, how many kilometers it has traveled and whether it is repaired or not, it should be recorded in detail so as to arrange replacement and replacement. I also have a bottom in my heart, which tire is what working condition); ⑦ The parameters and indexes of spare tires of ordinary cars (except luxury cars) are exactly the same as those of the four tires in use, and they can be used interchangeably when there is a problem with the tires.
However, it is strongly recommended to replace the damaged tires after repair. The spare tire is still used as a spare tire. Keep this tire intact for a long time in case of emergency.
If the repaired tire is used as a spare tire, it may appear that the tire is flat when trying to use the spare tire because of slow deflation. Moreover, the spare tire is relatively new and paired with the old tire, which also undermines the above principle of pairing.
Tire identification shall conform to national standards, and the production number, manufacturer's trademark, size specification, grade, maximum load and corresponding air pressure, Chinese phonetic code of carcass cord fabric, installation requirements and driving direction signs shall be marked on both sides of the tire. The material of the carcass cord fabric is expressed in Chinese Pinyin.
Such as M cotton, R rayon, N nylon, G steel and ZG steel radial tires. The tire side is marked with symbols such as △,-and □ or with words such as "W" and "D", indicating the lightest part of the tire. When installing the inner tube, the valve should be aligned with the symbol to make the weight around the tire uniform and maintain the stability of the tire when it rotates at high speed.
The arrow ""indicates a directional tire. Install in the direction of rotation indicated by the arrow.
The high-pressure tire is denoted by D5B, D denotes the nominal outer diameter of the tire, and B denotes the cross-sectional width of the tire in inches. "X" stands for high pressure tire.
The low-pressure tire is represented by B-d, where B is the tire section width, D is the rim diameter, and "-"represents the low-pressure tire. Since the section b is approximately equal to the section height h, the dimension d of the mounting rim can be calculated as d=D-2B.
For example, the tires for Audi cars are 185/80R 1490S. Tire section width and height ratio (flattening ratio) are two important indexes to describe tire size.
The tire section width refers to the maximum distance between the two outer sides after the tire is inflated according to regulations. Generally divided by 5mm, but the tolerance of new tire section width is 63%. The section width refers to half of the difference between the outer diameter and the nominal diameter of the tire inflated rear rim.
The tire height-width ratio (H/B) is the ratio of tire cross-section height H to cross-section width B, which is expressed by the fraction after rounding the diameter. Usually a multiple of 54. For example, automobile radial tires are divided into 60, 65, 70, 75 and 80 series.
The figure below shows the maximum driving speed of different tire structures. Maximum running speed (hm/h)101213120135150 radial tire q135/kloc.
English specification mark: this mark is used for ordinary cross-section truck tires and car bias tires. Mainly in the following parts.
The nominal section width of tire A is in the nominal diameter of C rim, which is the structural symbol in tire B.. The structure symbol of D-class radial tire is indicated by "R", and the structure symbol of bias tire is indicated by "-". The grade refers to the specific strength sign of the tire bearing the maximum load, and does not necessarily represent the actual number of plies. For example, for a 9.00 12 tire, there may be several actual layers, but the maximum load is 2050kg.
For example: 6.5R 16 6P.R. 6.5: tire nominal section width (6.5 in) R: radial tire logo 16: nominal rim diameter 6P. R: Tire grade is 6 (maximum load is 635 kg, corresponding air pressure is 3.50kg). Metric specification logo: This representation is used for general radial automobile tires. Include the following contents: the nominal section width of A tire is only the nominal height-width ratio of mm B tire, the nominal diameter of rim of C speed symbol D tire structure symbol E is inches, and the nominal height-width ratio of tire refers to the section height and section of tire installed on theoretical rim.
9. What are the four-wheel maintenance
Modern automobile wheel bearings mostly adopt maintenance-free oil-bearing which can't be disassembled, so they can't be cleaned and oiled.
Generally speaking: front and rear drum-type vehicles: the front wheel adopts oil-bearing with a general service life of about 8W km, which cannot be decomposed and maintained, and can be replaced after being damaged; The rear wheel adopts split cone bearing, an inner bearing and an outer bearing. The bearing can be disassembled and decomposed into two independent standard bearings. Cleaning and maintaining the bearing every 2 kilometers can improve the service life of the bearing. This structure is generally used in economical cars, such as Pu Sang, Sail, Jetta and Goyle.
Some rear drum cars also use oil-bearing such as Chang 'an and Fukang. Four-wheel disc brake car: Because all four wheels adopt oil-bearing structure, it is unnecessary and impossible to maintain the wheel bearings.
This structure is commonly used in middle and high-grade cars, such as Excelle, Buick, 307, Golf and Cheng Jing. So some cars only need to maintain two rear wheels, and some cars don't need and can't maintain four wheels at all. However, you should also correctly understand the knowledge of four-wheel alignment and regularly detect four-wheel alignment, so as to effectively reduce the safety hazards during driving.