When choosing new tires, many drivers do not think about their labeling or pay attention only to the size. However, the tire speed and load index is no less important than the diameter or width. You can read more about what the tire speed index means and how to choose the right tires.
Tire marking
It will be useful for any motorist to know the information that is located on the side of the tire. Usually, buyers pay attention only to the diameter and width of the rubber, while many other parameters can be found on it: from specifying the maximum permissible mass to weather conditions (rain or dry road). What markings can be distinguished?
- Tire size is the most important designation. It indicates the width of the profile, the bore diameter, the type of tire and the ratio of the height of the profile to its width. Here is an example designation: 195 / 60R14. There are no uniform labeling standards, so tires made in America have different characters.
- Maximum Load Index - shows how many kilograms tires can withstand on a car. This designation is usually indicated in the form of a cipher. The designation helps prevent tire damage from improper use.
- The following is usually the code for compliance with EU quality requirements. Each country has its own code.
- Maximum pressure is crucial for long-term use of tires. Experienced motorists know that under-loaded wheels can lead to deterioration of the technical characteristics of the machine, and excessively high pressure can cause damage to the wheels.
- Season and cover. With the help of these symbols, the type of tire is briefly indicated: all-weather, summer or winter. Weather conditions (rain, dry road, dirt) may also be indicated.
- Year of manufacture for determining the expiration date of tires.
- The wear indicator is a special groove that is closer to the TWID inscription and has a bright color. If the groove is completely erased and the color coating is not visible, then the tire needs to be replaced.
In addition to the designations listed above, on the side you can also find the speed index. Below you can find the decryption of the tire speed index.
What is a speed index
On any tires next to the tire size you can find numbers indicating the maximum permissible speed when using the product. What does the tire speed index mean? It indicates the maximum permissible degree of acceleration, which is not recommended to go anymore. It is easy enough to find this indicator, since it is located on the side of the tire next to the size designation. Marking is indicated by a letter or a combination of letters of the Latin alphabet. It is believed that truck drivers are the most interested in the tire speed index, who often travel long distances and try to squeeze more out of the car to save time. But for car owners, this information may be relevant: following the recommendations for use significantly extends the life of rubber.
What is affected by the speed index and load index?
In the manufacture of tires, car manufacturers follow generally accepted standards applicable to certain vehicles. The speed index indicates what speed the wheel can withstand under load. What is affected by tire speed index? First of all, proper tire selection and adherence to recommended speeds can significantly extend tire life. By following the directions on the rubber rim, you reduce the likelihood that they will fail you at the most inopportune moment. For example, if the speed limit of 130 km / h is indicated on the tires as the maximum permissible speed mode, then a long ride at 160 km / h can deform tires. If you drive "with disabilities" by force an hour a year, then, of course, this will not have a noticeable effect on the quality of the rubber.
Speed Markings
The maximum tire speed index is indicated by Latin numbers. For quick decryption, you can remember the most common designations - it is “N” and “P”, they are most often indicated on the wheels for passenger cars. Decoding tire speed indices:
- The letter "N" - 140 km / h;
- The letter "P" - 149 km / h;
- The letter "Q" - 159 km / h;
- The letter "R" - 170 km / h;
- The letter "S" - 180 km / h;
- The letter "T" - 190 km / h;
- The letter "U" - 200 km / h;
- The letter "H" - 210 km / h;
- The letter "V" - 240 km / h;
- The letter "Z" - 241 km / h;
- The letter "W" - 270 km / h;
- The letter "Y" is 300 km / h.
As a rule, standard designations for cars do not reach 150 km / h. This makes no sense, since the maximum speed of cars ranges from 110 to 130 km / h. For those who like to travel fast, special high-speed tires are developed that can withstand a long ride at speeds of 160 and above. Tires labeled “Q” and “R” are useful for this. The remaining tires are more likely for race car drivers who can accelerate their car to a speed of 210 or even 300 km / h. In these cases, when choosing the right wheels, you can not be afraid that they will fail at that speed.
Tire load index
The load index is firmly linked to the passenger tire speed index. It indicates how many kilograms one wheel can support. This parameter is especially relevant for truck owners, since they definitely need to know how much the machine can withstand without harming its parts. For heavy vehicles that are designed to carry goods, they produce special tires with increased requirements for the material from which they were made. As a rule, such tires are much thicker than usual, and when driving they make a lot of noise. Wheels designed for heavy loads, consume more fuel and affect the speed of acceleration of the car. Therefore, experts do not recommend buying them "just like that." Rubber with a lower load index, on the contrary, provides a smoother ride. Such tires are almost inaudible in the cabin, they reduce the load on the suspension and other car designs. In addition, they are much lighter, which means that the car accelerates more easily and consumes less gasoline. Therefore, before buying a wheel, carefully study the tire load index and select the ones that are more suitable for you.
The tire load index is indicated by a number and the abbreviation "PR", which indicates the marking of ply. For passenger cars often produce tires with an index of 4PR or 6PR. If you see such tires in the store, feel free to take them. If you have a minibus, then you should take a closer look at the wheels marked 6PR or 8PR. For heavy trucks produce rubber with a special composition, which is marked with the letter "C" ("commercial transport").
Relationship between load index and tire speed
What is the relationship between load index and tire speed? The maximum speed directly depends on the permissible load. After all, the higher the speed, the more effort falls on the wheels. That is why this parameter must be carefully observed - it guarantees driving safety. Otherwise, the tire may burst sooner or later, and the car will be seriously damaged.
The higher the speed of the car - the less should be the load on the tires. For example, if there is a “U” marking on the wheel rim, which indicates a maximum speed of 200 km / h, then up to this figure the machine can be loaded “in full”. But if the driver is already driving 210 km / h, then the load on the wheels should decrease by 4%.
How to choose the right tires
It is impossible to select wheels without taking into account the speed index of passenger cars and the load index. When choosing tires, you need to consider the size of the rubber, seasonality. If you are in doubt about whether these tires are suitable for you, it is best to consult a specialist. They know many of the nuances and characteristics of the wheels that can make traveling by car more economical and more enjoyable. If you are used to choosing the product yourself, then you can find out the recommended parameters for your machine by looking at the operating instructions or contacting the manufacturer directly.
Expert Advice
In order to avoid damage to tires, experts advise to observe the following conditions:
- Follow the recommendations for the maximum permitted speed.
- Do not install wheels with a speed index lower than that recommended by the manufacturer.
- Do not install racing tires on ordinary cars.
By following these simple rules and choosing tires according to the recommendations, you will extend the life of your car and avoid expensive repairs.
Summary
The parameters that indicate the load, as well as the speed index of truck tires and cars, are extremely important when buying new rubber. Ignoring the recommendations indicated on the tire rim, one may encounter not only a deterioration in the technical characteristics of the car, but also an expensive repair. That is why every driver needs to know what the load index and maximum speed are, and follow the above recommendations.