type of tire

International standard tire code, expressed in millimeters as a percentage of section height and aspect ratio. Add: tire type code, rim diameter (inch), load index (allowable bearing quality code), allowable speed code. For example: 175/70R 14 77H in 175 means the tire width is 175MM, 70 means the aspect ratio of the tire section is 70%, that is, the section height is 70% of the width, the rim diameter is 14 inches, the load index is 77, and the allowable speed is H class.

How to identify tire specifications

General tire specifications can be described as:

[Tire width mm]/[The percentage of tire thickness and tire width] R[Wheel diameter (inch)] [Load factor][Speed ​​mark]

  or

[Tire width mm]/[The percentage of tire thickness and tire width][Speed ​​mark] R[Wheel diameter (inch)] [Load factor]

Example tires: 195/65 R14 88H or 195/65H R15 88

can be interpreted as:

Tire width -----------------------195mm

The percentage of tire thickness and tire width is -------65%, that is, tire thickness=126.75, 126.75/195*100=65(%)

Wheel diameter-------------------15 inches

Load factor-------------------88

Speed ​​coefficient-------------------H

Generally speaking, it is helpful to know [tire width]/[the percentage of tire thickness and tire width] R[wheel diameter (inch)] to change the tires suitable for your car. Know the tire's [load factor][speed mark] Helps with driving safety.

Tire speed marking table

Speed ​​sign Maximum speed Common models

N 140km/h Spare Tires

P 150km/h

Q 160km/h snow tires, light truck tires Winter, LT Tires

R 170km/h Light Truck Tires LT Tires

S 180km/h

T 190km/h

U 200km/h

H 210km/h Sport Sedan Sport Sedans

V 240km/h Sports Cars Sports Cars

Z 240km/h Sports Cars (or more than 240km/h)

W 270km/h Exotic Sport Cars

Y 300km/h Exotic Sport Cars

  Note:

1. The more common tire speed signs are, S, T, H

2. If there is no speed mark on the tire, unless otherwise stated, the maximum safe speed is generally considered to be 120KM/H.

The following are some common signs on tires, the picture is a typical North American tire mark for reference only.

Tire Size/Tire Size, Loading Rating Index/Load Factor, Speed ​​Rating Index/Speed ​​Mark.

Car wheels generally use radial tires. Specifications for radial tires include width, aspect ratio, inner diameter, and speed limit symbols. Take the Toyota CROWN 3.0 sedan as an example, its tire size is 195/65R15, which means the width between the two sides of the tire is 195 mm, 65 means the aspect ratio, and "R" stands for the word RADIAL, which means it is a radial tire. 15 is the inner diameter of the tire in inches. Some tires are also marked with speed limit symbols, and letters such as P, R, S, T, H, V, Z are used to represent each speed limit value.

In particular, the aspect ratio should be pointed out, which means that the height of the tire sidewall accounts for the percentage of the tire width. The tire aspect ratio of modern cars is between 50 and 70. The smaller the value, the flatter the tire shape. As the speed of the vehicle increases, in order to lower the center of gravity and axis of the car, the diameter of the tire continues to shrink. In order to ensure sufficient carrying capacity and improve driving stability and grip, the width of tires and rims has to be continuously increased. Therefore, the cross-sectional shape of the tire develops from the original approximate circular shape to a flattened oval shape.

In recent years, the car has realized the radial tire tubeless, commonly known as "atom tire". This kind of tire is not easy to accumulate heat during high-speed driving. When the tire is pierced by a nail or a sharp object, the air leakage is slow, and it can continue to drive for a certain distance. In addition, atomic tires have the advantages of simplifying the production process, reducing weight, and saving raw materials. Therefore, the assembly of atomic tires has gradually become a trend in the field of cars.

Tire specification classification

At present, there are many ways to express the specifications of tires, and there are four common ones on the market, British, German, metric and American, we will briefly explain the next four.

The imperial system was adopted by the former vassals of the United Kingdom, and the unit is inches. For example, 4.00 H 18 4PR means that the width is 4 inches, which is suitable for the speed below 210KM/H, the diameter of the tire rim is 18 inches, and the strength of 4 wire layers. In the metric notation, the description of the characteristics of the tire is relatively complete at present. It is similar to the German notation, but the symbol of "-" low pressure tire is cancelled, and the word "R" is used instead to indicate the radial tire, such as The rear wheel of FZR400 is 140/60R18 64H, and the R of R18 means that the tire is a radial tire.

The German-made specifications are similar to the "metric system", except that the width of the tire is expressed in millimeters, and the aspect ratio of the tire is also increased. The inner diameter of the tire is still in inches, and there are load index and speed marks behind the inner diameter. Indicates such as: 140 (tire width 140MM) 70 (flat ratio 70%) - (low tire pressure) 18 (inner diameter 18 inches) 66 (load index 66) H (speed mark below 210KM/H).

The prefix of the US standard indicates that the tire is suitable for the vehicle type, the second letter indicates the width of the tire, the third letter indicates the flat rate, the fourth letter is the speed mark, and finally the diameter of the steel rim.

Among them, the value of the load index table J ranges from 21 to 74. The larger the value, the stronger the load capacity. Generally, the J value is about 63~67 for heavy vehicles of 400cc to 750cc, and the front wheel is about 57~58; in addition The speed symbol K of a tubeless wheel is the maximum speed that the tire can bear, expressed in English letters, the later the letter is, the higher the allowable speed limit is, S: the table is suitable for below 180KM/H; H: the table is suitable for 210KM/ H below; V: the table is suitable for 210KM/H and above; S, H, V are all visible to ordinary vehicles, and they are also called high-speed tires. Usually, if the tires are lower than the above speed marks, they are not marked with speed marks. Therefore, as long as we see the speed mark after the S letter, it can be regarded as a high-speed tire. Vehicles with a low aspect ratio have shorter sidewalls, so the tread becomes very wide for the same diameter. In this way, the ground contact area can be increased, the pressure that the tire can bear is also large, and the response to the road surface is very sensitive, while the tire with a high flat ratio has sufficient buffer thickness, but the feeling of the road surface is poor, and the lateral resistance when turning Weak and unable to have very stable performance. When the locomotive is turning at high speed, the body must have a large roll, so the lateral stress is small, and in order to consider the small bumps and grooves of the tire, the vibration can still be absorbed calmly, so the 80% low flat radiation tires to maximize its performance.

The ratio of the maximum width measured from the section of the tire to the height of the rim to the tread is the aspect ratio, expressed as a percentage, that is, the percentage of the height to the width. Performance imitation racing cars also use tires with a high aspect ratio of 70 to 60. Commercially available tires also begin to appear in this wide-faced, low-aspect-ratio vehicle. Due to the large lateral shearing force of the car when turning, even ultra-low flat tires with a flat ratio of 45% will appear in a four-wheel sports car, but the average sports car is still between 50 and 55. in order to maintain comfort.

Front tire specifications

As the name suggests, it is the size of the front tire of the car; the front and rear tires of most cars are the same. In a few high-performance special-purpose vehicles such as sports cars and rear-wheel drive, the front and rear tire specifications will be different.

If the displacement is used as the measurement standard, in general, the larger the displacement model, the larger the tire size will be. Of course, the size of the tire will directly affect the comfort and appearance of the vehicle, as well as its passing performance.

International standard tire code, in millimeters to indicate the percentage of section height and aspect ratio, followed by: tire type code, rim diameter (inch), load index (allowable bearing quality code), allowable speed code. E.g:

In 175/70R 14 77H, 175 means the tire width is 175MM, 70 means the aspect ratio of the tire section is 70%, that is, the section height is 70% of the width, the rim diameter is 14 inches, the load index is 77, and the allowable speed is H level.

The displacement of the small car is between 0.8-1.5. The corresponding front tire specification is applicable to the range of 155/65R13 73T--175/70 R 14 77H.

The small size of the front tires reduces the friction between the vehicle and the ground, so it is more economical in terms of fuel. This is the main reason why most consumers choose small-displacement cars, but the resulting negative impact is , because its tread diameter is limited, it will greatly reduce its passability and comfort, and often when driving a small-displacement car over the ridge, you will feel at a loss. Small-sized tires make the steering more brisk. There is no power steering in the sedans.

The tire size of the large car is between 1.6-6.0 and the corresponding tire size is in the range of 185/60 R 14-- 245/50 R 18.

The large-sized tires will make the whole body look domineering, and the good adhesion to the ground ensures its acceleration performance and body stability at high speeds.

The specifications of the front and rear tires of some special off-road vehicles and modified racing vehicles may vary. Generally, they will be designed with a small front and a large rear. If it is a four-wheel drive model, it will also involve the problem of the inter-axle differential, because the front and rear The size of the wheels is different, and the traveling of the car will be affected. When the car is walking on the ground, the time it takes for the rear wheels to make a circle will be longer than that of the front wheels, which will affect the normal movement of the front and rear axles.

Rear tire specifications

The rear tire specification, as the name suggests, is the size of the rear tire of the car; the front and rear tire specifications of most cars are the same. In a few high-performance special-purpose vehicles such as sports cars and rear-wheel drive, the front and rear tire specifications will be different.

For example, in the annual modified car competition in California, the United States, some riders will modify the specifications of their front and rear tires differently, so that the front and rear tires will have a diameter difference of 1-2 meters, highlighting their own uniqueness. , the driver's dress is also quite distinctive, giving people a very "alternative" feeling.

It is more convenient for two-wheel drive models to carry out this modification, because the problem of the inter-axle differential will not be involved in the modification process, and even if the specifications of the front and rear tires are different, it will not affect the normal driving of the vehicle.

If the four-wheel drive model is to be modified with different front and rear tire specifications, it will be a lot of trouble compared to the two-wheel drive model. There will be a speed difference between the two. If the inter-axle differential is not installed, the two wheels will "compete" with each other, so the vehicle will not run normally, causing serious damage to the tires and the drive shaft!