A journey of a thousand miles begins with a single step. As the four legs of an automobile, the importance of automobile tires is self-evident. In the process of high-speed driving, tire failure is the most worrying and difficult to prevent for all drivers, and it is also an important reason for sudden traffic accidents. Tires are an important part of a car's driving system. Just like the shoes we wear, we should not only choose them correctly according to their functions (don't wear formal shoes to play tennis or sports shoes to dance the national standard), but also know how to take care of them. Let's explore the mystery of tires together.
The common tire classification method is divided into diagonal tire and radial tire according to the structure. The fundamental difference between radial tire and bias tire lies in the carcass. The carcass of the diagonal tire is a diagonal ply; The carcass of radial tire is made of polymer multi-layer cross material, and its top layer is several layers of steel belt cord fabric made of steel wire, which can reduce the probability of tire being punctured by foreign objects.
In terms of design, bias tire has many limitations. For example, due to the strong friction of the crossed cords, the carcass is prone to heat generation, which accelerates the wear of tread patterns, and its cord layout cannot provide excellent handling and comfort. The steel wire belt in radial tire has good flexibility to adapt to the irregular impact of the road surface, and it is durable. Its cord structure also means that there is much less friction than the diagonal line when the car is driving, thus obtaining a longer tread life and better fuel economy. At the same time, the characteristics of radial tire itself make it possible to have a tubeless tire. The tubeless tire has a recognized advantage, that is, when the tire is punctured, it will not burst like the diagonal tire with inner tube (which is very dangerous), but it can keep the air pressure for a period of time, which improves the driving safety of the automobile. In addition, compared with diagonal tire, radial tire has better grip.
The tires we are talking about below only refer to radial tires commonly used in cars at present, commonly known as vacuum tires or atomic tires.
1. How to identify tire marks
Tire is an important part of automobile, and there are more than 1 kinds of marks on automobile tires. Correctly identifying these marks is very important for the selection, use and maintenance of tires, and is of great significance for ensuring driving safety and prolonging the service life of tires.
tyre size: Specification is the symbolic data of tire geometric parameters and physical properties. Tyre size is usually represented by a set of numbers, with the former number representing the tire section width and the latter number representing the rim diameter, all in inches. The letters or symbols in the middle have special meanings: "X" stands for high-pressure tire; "R" and "Z" represent radial tires; "One" means a low-pressure tire.
hierarchy: hierarchy refers to the nominal number of plies in the rubber layer of a tire, which is not completely consistent with the actual number of plies, and is an important indicator of tire strength. Levels are marked in Chinese, such as 12 levels; Mark in English, such as "〃14P．R〃", that is, 14 poles.
cord material: some tires are marked separately, such as "NYLON", which is usually marked after the hierarchy; Some tire manufacturers in the world mark the specifications with the first letter of Chinese Pinyin, such as 9.－2N, 7.5－2G, etc. N stands for nylon, G stands for steel wire, M stands for cotton thread and R stands for rayon.
load and air pressure: generally, the maximum load and the corresponding air pressure are indicated, and the load is in kilograms, and the air pressure is the tire pressure in kilopascals.
rim specification: indicates the rim specification matched with the tire. Convenient for practical use, such as "standard rim 5.F".
balance mark: it is made of colored rubber and printed on the sidewall, indicating that the tire is the lightest here, and it should be assembled right against the valve to ensure the balance of the whole tire.
rolling direction: the tread pattern on the tire is particularly critical to the drainage and skid resistance during driving, so the off-road vehicle tires with asymmetrical tread patterns are often marked with arrows to indicate the rolling direction, so as to ensure the designed adhesion and skid resistance. If it is installed incorrectly, it will be counterproductive.
wear limit sign: the wear limit of the tire is marked with rubber strip and block on one side of the tire. Once the tire reaches this sign position, it should be replaced in time, otherwise it will burst halfway due to insufficient strength.
production batch number: a set of numbers and letters are used to indicate the year, month and quantity of tire manufacture. For example, "98N8B582" means the 582th tire produced by Group B in August 1998. The production batch number is used to identify the newness and storage time of tires.
trademark: a trademark is a symbol of a tire manufacturer, including trademark words and patterns, which are generally prominent and eye-catching and easy to identify. Most of them are marked with the name of the manufacturer.
other marks: such as product grade, production license number and other subsidiary marks. It can be used as reference materials and information when selecting.
Generally, tire markings are standardized, so you can choose and use them with confidence after being clearly identified.
The following is a common tyre size representation:
Example: 185/7R1486h
185: tread width (mm)
7: flatness ratio (tire height ÷ tire width)
R: meridian structure
14: rim diameter (inch How to choose tires
Knowing the basic knowledge of tires is only the first step. The next step is to consider how to buy tires suitable for your car. When choosing, you should not only know the tyre size your car needs, but also pay attention to the following aspects.
First, give priority to the original tires, which can best match the speed and maximum load of the car. Therefore, in theory, it should be given priority when replacing tires.
Secondly, pay attention to the tire pattern. The pattern on the automobile tire not only plays a beautiful role, but also has a great influence on the performance of the tire. Cars that often drive in Shenzhen should choose those patterned tires with good drainage, such as regular small block patterns; For cars that need cross-country and long-distance running, you can choose large patterns.
finally, if you are not satisfied with the original handling of the vehicle, you can consider replacing the tires with lower flat ratio. For many models, one of the most effective ways to improve the appearance and handling performance of the vehicle is to replace the tires with lower flat ratio. Every type of tire has its specific function, so when choosing a tire, you should ask what type of tire is suitable for what kind of driving habits, so that the car is safer when driving and the money spent on the tire is more worthwhile.
when buying tires, don't just look at the price, but ask professionals, who will help you match the right tires accurately.
when choosing tires, you should also pay attention to never mixing different types of tires, such as putting tires suitable for off-road vehicles with tires of ordinary cars, or mixing directional sports car tires with ordinary tires.
Of course, we should try our best to avoid retreaded tires when shopping. At present, some retreaded tires are often sold as inferior products in Shenzhen, especially in some street shops, so consumers must pay attention to them when shopping. The method of identifying retreaded tires is simple: the most common thing is to observe the color and luster of the tires. The color and luster of the retreaded tires are dim, so don't blindly buy such tires.
Professional masters identify tires by the marks on the tires. There are some protruding marks on automobile tires, which indicate the model and performance of tires. These are the breakthrough points in identifying retreaded tires. Signs of retreaded tires are re-attached after retreading, while these signs of brand-new tires are integrated with the tires. The identification method is to scratch these signs with fingernails. Generally, these signs of retreaded tires are not tightly attached, and the ones that can be caught must be retreaded tires.
in recent years, the development trend of foreign car tires is to use more and more tires with large width, large inner diameter and low flatness ratio. At present, domestic cars mostly use tires with small width, small inner diameter and high flatness ratio. The tire with high flatness ratio has relatively high comfort because of its long sidewall and strong cushioning ability, but it has poor feeling on the road surface and weak lateral resistance when turning. On the other hand, tires with low flat ratio and large inner diameter have short sidewall and wide tread. Therefore, the ground contact area is large, the tire can bear great pressure, it is very sensitive to the road surface and has strong lateral resistance when turning, which greatly enhances the handling of the vehicle. At present, the tire with the largest flat ratio used in domestic mass-produced cars is 225／55R16, while the tires of many imported luxury cars or sports coupes reach 225／45R17, and some even reach 245／4R18. After the vehicle is equipped with tires with large width, large inner diameter and low flatness ratio, in addition to strong maneuverability, the visual effect of appearance also gives people a very powerful feeling. Generally speaking, the tires equipped with vehicles are the best specifications selected by manufacturers after repeated tests. If a car owner wants to change the tire size, it must be done under the guidance of professionals, and it can't be done at will, because it involves many problems, and a little negligence may cause harm to driving safety. In addition, low flat ratio tires will be more "delicate" and should be paid more attention to and cared for during use.
what is the speed grade of the tire?
A: Officially, the speed class indicates the maximum speed at which a tire can bear a specified load under specified conditions. The letters A to Z represent the certified speed classes of tires from 4.8 km/h to 3 km/h.. Commonly used speed grades are:
Q 16 km/h V 24 km/h
R 17 km/h W 27 km/h
S 18 km/h Y 3 km/h
T 19 km/h, Z ZR speed is higher than 24 km/h
H 21 km/h. For example, P275/4ZR17 93W, the highest speed level ("W" in "93W") is 27km/h..
In the recent regulations for standardization of tire identification, the speed symbol and load factor are included in the instructions for all grades except the stepless speed Z speed grade. For example, P225/6R15 95H is the instruction of the tire, indicating that the maximum load capacity of the tire is 69kg and the maximum speed grade is 21km/h..
q: I'm going to buy two new tires. Should I install them on the front or rear wheels?
a: the rear wheel. When turning sharply on wet road, if your front wheel slips first, your car will continue to walk in a straight line even when turning. This is equivalent to understeer, and you can slow down and then turn along the curve. This will get the car back in the driveway.
but if the rear wheel slips first, the car may flick its tail, which is equivalent to oversteer and will only be more difficult to control. This requires you to make a quick and accurate steering correction in the opposite direction of the curve, which is not a natural reaction. It is easier to control understeer than oversteer.
in order to keep records, the best choice is to buy four new tires of the same brand, specification and model at a time when changing tires.
q: if I only want to buy one tire, what product should I buy and where should I install it?
a: the only proper reason to buy only one tire is to replace the tire damaged by accidents or road hazards, otherwise all four tires in the set will be good. When purchasing, you should look for the same specification, model, brand and tread pattern design as the replacement tire. Replacing Four Seasons Tire with Four Seasons Tire. Replace snow tires with snow tires. Replace the tires of H speed class with those of H speed class. In this way, you will enjoy a safer and more comfortable driving experience.
Q: Skills of tire use
① Ordinary automobile tires have no directionality, and in principle they can be interchanged left and right (unlike F1 racing tires, which have strict directionality);
② Jetta suggests that the front and rear tires should be used interchangeably every 2,KM (Fei Xian: I read the literature that the rear wheels can be moved to the front in parallel, and the front wheels can be crossed to the back. The reason is that in general, the wear of automobile tires is greater in the front than in the back, because there is steering action in the front; The right side is larger than the left side, because the road is curved, and the tire stroke on the right side will be longer. ）；
③ The aging of tires is not obvious, and the aging and wear, mileage and road conditions account for most of the reasons; That is to say, the driving years should not be used as the standard to judge whether to replace the tires, but the mileage should be used as the main parameter, and the most important thing is the degree of tire wear (Fei Xian: unfortunately, I can't find a map now, which can clearly indicate which pattern must be replaced as soon as possible, please look for it in DX);
④ it is not good to enlarge the hub blindly, and the braking effect will be worse. Because the braking force of the braking mechanism may be insufficient;
⑤ The comfort and stability are enhanced by using tires that are too wide, but the fuel consumption increases, and there will be problems in braking;
⑥ tires should be used and replaced in pairs as far as possible, and the left and right balance of the vehicle can be ensured by keeping a pair of tires in similar wear and working conditions (Fei Xian: when each tire was replaced, how many kilometers it was and whether it was repaired 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 indicators of spare tires of ordinary cars (except luxury cars) are exactly the same as those of the four tires in use, and can be used interchangeably when there is a problem with the tires. However, it is strongly recommended to replace the broken tire after repairing it. 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 happen that the tire is flat when you want to use the spare tire because of slow deflation. Moreover, the spare tire is relatively new, and it is paired with the old tire, which also undermines the above principle of paired use.
tire identification
according to the national standard, 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 marks should be marked on both sides of the tire.
The carcass cord material is expressed in Chinese Pinyin. Such as M- cotton, R- rayon, N- nylon, G- steel and ZG- steel radial tire.
symbols such as △,-,□ or words such as "W" and "D" are marked on the side of the tire, indicating the lightest part of the tire. When installing the inner tube, the valve should be aligned with the symbols to make the weight around the tire even and keep the tire stable when rotating at high speed. An arrow ""indicates a directional tire. Install in the direction indicated by the arrow as the rotation direction.
the high-pressure tire is represented by D5B, where d represents the nominal outer diameter of the tire and b is 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 installed rim can be calculated as d=D-2B. For example, the tires used in Audi cars are 185/8R149S.
The tire section width and height ratio (flatness ratio) are two important indicators to describe the tire size.
the tire section width refers to the maximum distance between the two outer sides after the tire is inflated according to the regulations, which is generally divided by 5mm, but the tolerance of the new tire section width is 63%.