Choosing the right tires for your car is not just a matter of comfort, but a critical safety aspect that directly affects the vehicle's road grip and handling. The sidewall of any tire contains a complex set of symbols, numbers and letter codes that tell about its technical characteristics, maximum operating conditions and design features. Understanding this data allows the car owner to avoid fatal mistakes when purchasing, excluding the installation of products that do not comply with the recommendations of the car manufacturer.
Often drivers pay attention only to the standard size, ignoring the load and speed indices, which can lead to tire destruction under extreme loads or overheating at high speeds. In this article, we will analyze the labeling structure in detail, explain the meaning of each element, and provide reference tables for quickly checking parameters. You'll learn to read a wheel's datasheet as easily as you read words, helping you make informed choices at the store every time.
Basic size structure and seasonality
The most noticeable part of the marking, located on the outside of the sidewall, is the standard size. It is a combination of numbers and letters, e.g. 205/55 R16 91H. The first number (205) indicates the profile width in millimeters. The second number (55) is the ratio of the profile height to the width, expressed as a percentage. It is important to understand that the profile height is calculated based on the width, and is not an absolute value in millimeters.
Letter R in the center of the designation indicates a radial cord design, which is the standard for modern passenger cars. Previously, there were diagonal tires, but now they are practically not found in the civilian segment. The number 16 is the wheel diameter in inches. An incorrect selection of diameter will make installation physically impossible, so checking this parameter is mandatory before purchasing.
Seasonality marking, which is often lost among other symbols, deserves special attention. Winter tires are characterized by the presence of a snowflake inside a mountain peak (3PMSF) or a letter M+S (Mud + Snow). Summer tires do not have such designations, but may contain markings Summer or Outside for asymmetric tread pattern. All-season models are marked as All Season or AS, however, their effectiveness is inferior to specialized analogues in extreme conditions.
⚠️ Attention: Installing winter tires with a speed index lower than that recommended by the car manufacturer is permissible only if the driver strictly adheres to the speed limit and sticks the appropriate sticker on the dashboard.
Load and speed indices: correspondence table
The tire size is followed by a numeric and alphabetic code, e.g. 91H. The number 91 is a load index showing the maximum permissible weight that one wheel can support when moving. The letter H denotes a speed index indicating the maximum speed at which the tire maintains its performance characteristics. Exceeding these limits leads to sudden heating and possible tire explosion.
Load and speed indices are not linear, so special tables must be used to decipher them. Below are the most common values for passenger cars. When selecting tires, always choose values equal to or higher than those specified in the technical documentation of your car.
| Load Index | Load (kg) | Speed index | Speed (km/h) |
|---|---|---|---|
| 88 | 560 | T | 190 |
| 91 | 615 | H | 210 |
| 94 | 670 | V | 240 |
| 98 | 750 | W | 270 |
| 102 | 850 | Y | 300 |
There is also the concept of XL (Extra Load) or Reinforced, which indicates a reinforced sidewall structure and an increased load index. These tires are stiffer than regular tires, but provide better stability when the vehicle is fully loaded. If you frequently carry heavy loads or travel with a full passenger load, choosing tires rated XL will make a better safety decision.
Design features and additional markings
Modern tire production technologies involve the use of various improvements, which are reflected in additional letter designations on the sidewall. One of the most common technologies is RunFlat (or RSC, ZP, SSR for different brands). These abbreviations mean that the tire has reinforced sidewalls and allows you to travel a certain distance (usually up to 80 km) with zero pressure at speeds up to 80 km/h.
Another important parameter is the direction of rotation, especially for winter and rain tires. There is always an arrow on the side of such models Rotation, indicating the direction of rolling. Installing such a tire in the opposite direction will lead to the fact that the tread will not effectively remove water and slush from the contact patch, which will sharply increase the risk of aquaplaning.
You can also find cord type designations, for example, TW (Textile) or PL (Polyester), although for the average user this is more of a reference. More important is the Tubeless designation, which means tubeless design, or Tube Type, which requires the installation of a camera. Almost all modern passenger tires are tubeless, which provides better sealing and lower weight of the wheel assembly.
What do the colored marks on the tread mean?
You will often notice colored dots or stripes on new tires. A yellow dot or triangle indicates the lightest point of the tire; during installation, this mark is aligned with the wheel nipple (the heaviest point) for better balancing. The red dot indicates the place with maximum force heterogeneity; it is combined with the white dot on the disk (if there is one). The multi-colored lines on the tread itself are just factory markings for warehouse logistics; they are erased in the first hundreds of kilometers and do not carry technical information for the driver.
Production date and rubber service life
Determining the release date of a tire is a critical skill when purchasing, especially if you purchase tires not from a specialized center, but from the market or “from hand.” The rubber compound ages over time, losing elasticity and cracking, even if the tread looks new. The production date is stamped in an oval stamp on the side and consists of four numbers, e.g. 3523.
The first two digits indicate the week of production, and the second two indicate the year. In our example (3523), the tire was manufactured in week 35 of 2023. Some older models may have a three-digit code, with the year represented by a single number, indicating production in the 90s or earlier. It is not recommended to buy tires older than 5-6 years from the date of production, even if they have never been used, since the chemical composition of the rubber degrades.
☑️ Check before buying used tires
⚠️ Attention: Tires should be stored in a vertical position with periodic rotation to avoid deformation under their own weight. Horizontal stacking is only permissible for complete wheels (with rims).
Specific designations of car manufacturers
Many automakers order tires with unique compound and carcass settings tailored to specific vehicle models. Such tires have a special marking in the form of a letter code after the size. For example, the BMW concern uses the designation Star (asterisk), Mercedes - MO or MO1, and Porsche - N0, N1, N2 and so on.
Use of tires with the markings of a specific car manufacturer (Original Equipment) guarantees that the car will behave on the road exactly as the engineers intended when developing the suspension and stabilization systems. However, if you find an identical model without factory markings, it will also work, but may differ in harshness or noise level, which is especially noticeable on premium cars.
There are special tires for electric vehicles with markings EV or specific codes (for example, HN at Hankook). They have a reinforced frame to support the heavy weight of the batteries and an optimized composition to reduce rolling resistance and noise levels, since an electric vehicle does not have the noise of an internal combustion engine.
When replacing tires, try to buy a complete set of four identical tires. If this is not possible, on all-wheel drive vehicles (4WD/AWD), the difference in tread depth between the axles should not exceed 2-3 mm, otherwise the center differential may be damaged.
American and European labeling systems
Although the European metric system (for example, 205/55 R16) is the most common in the world, in the market, especially when ordering tires from the USA, you may encounter American standards. There are two types of American labeling: P-metric (starts with P, e.g. P205/55R16) and LT-metric (starts with LT, which stands for Light Truck). LT tires are designed for light trucks and have a stiffer sidewall.
Also in the USA, an inch size designation system is used, typical for off-road tires, for example, 31x10.5 R15. Here 31 is the outer diameter of the tire in inches, 10.5 is the section width, and 15 is the seat diameter. Converting such dimensions to metric requires the use of coefficients, since 1 inch is equal to 25.4 mm.
Another difference is the system for assessing traction qualities and temperature resistance UTQG (Uniform Tire Quality Grading), which is applied to the sidewall of tires sold in North America. It includes three parameters: Treadwear (wear resistance), Traction (grip) and Temperature (heat resistance). The higher the Treadwear number, theoretically the tread will last longer, although this data is often marketing in nature and depends on testing conditions.
The main rule of selection: always rely on the recommendations of the car manufacturer, indicated on the sign in the doorway or in the instructions, and not just on the sizes of the already installed wheels, since the previous owner may have installed non-standard tires.
In conclusion, it is worth noting that a careful study of the sidewall of a tire provides comprehensive information about its capabilities and limitations. Ignoring the markings can cost not only money for a new kit, but also your health. Regularly check the condition of the rubber, pressure and compliance of parameters with factory recommendations.
Is it possible to put tires with different speed ratings on one axle?
Strictly prohibited. Tires with the same tread pattern, size, load and speed indices must be mounted on the same axle. The difference is only allowed between the front and rear axles, while the “faster” tires must be placed on the rear axle to prevent skidding.
What do the words "Outside" and "Inside" on a tire mean?
This is a marking for an asymmetrical tread pattern. The side labeled "Outside" (or Side Facing Out) should face outward of the vehicle, and the side labeled "Inside" (Side Facing In) should face inward, toward the suspension. You cannot mix them up, otherwise the tire will not work correctly.
How often should tires be changed, even if the tread is deep?
Experts recommend changing tires every 5-6 years of operation due to the aging of the rubber compound, even if the tread depth is still high. After 10 years from the date of manufacture, the operation of any tire is considered unsafe.
Does the color stripe on the tread affect balance?
No, the colored lines on the tread itself are just factory markings for logistics and model identification in stock. They do not affect the balance, unlike the colored dots on the sidewall.