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Tire labeling: this is how you read a tire

Car tires have different names and symbols. These tire names are important for drivers, that's what they mean, that's what the vehicle documents say. Also: This is how winter tires are labeled.

The tire size in the vehicle documents

The "Registration Certificate Part 1" tells you which tire sizes are approved for the vehicle. Pay attention to lines 15.1 and 15.2 (see picture). Only one size combination is entered here. If different tire dimensions are provided on the front and rear axles, the information in the two lines will differ. The entered tire sizes do not have to match the actually installed tire dimensions.

Further possible tire sizes can be found in the so-called CoC document ("Certification of Conformity") under the numbers "32. Tires of the wheels" and / or "50. Comments". The CoC is part of the vehicle documents and can be requested from the brand dealer if necessary. You may only mount tire dimensions that deviate from the specifications in the registration certificate if you can find the wider variant in your CoC papers or in the manufacturer's series tire catalog.

Alternatively, tested and certified conversions can also be carried out. It is essential to ask a tire specialist about this and about possible requirements.

Tire sidewall: read letters, numbers and symbols correctly

The legal regulations for car tires are laid down in Section 36 of the StVZO. We'll tell you how to correctly read the letters, numbers and symbols.

Tire width

The tire width is always given in millimeters (here: 225 mm). In the case of car tires, the cross-sectional widths range from nominally 125 mm to approx. 335 mm. The widths increase in 10 mm steps.

The actual tire width may differ slightly from the nominal information. In addition, it is of course dependent on the width of the rim on which the tire is mounted.

The standardization of tires makes it possible to mount most tires on rims of different widths. However, it may be the case that only tires in combination with certain rims are permitted on certain vehicles. The use of snow chains can also be tied to certain tire and rim widths. Please note the information in the vehicle documents and in the operating instructions for the vehicle.

Height-to-width ratio

This is about the ratio of tire height to tire width in percent. A 70 means that the tire cross-section is 70 percent of the tire width. A 50 means that the tire height is half the tire width. The expert also speaks of series 50 or 50 series tires.

As the ratio falls, for example 225/45, the tire sidewall becomes lower and lower - a typical appearance of sporty or tuned cars.

Tire type

R stands for radial (often also written out in full). It is the construction that is common today with radially arranged carcass threads - the supporting skeleton of the tire. The previously common diagonal tires, marked with a D, are only allowed to be used on classic cars today.

If the letter R is followed by an F, it is a run-flat tire. In principle, only tires of one type may be mounted on cars. Mixed tires are not permitted; exceptions are permitted under certain circumstances.

Rim diameter

The number after the letter stands for the rim diameter. The rim diameter is measured on the ring on which the tire bead rests on the rim, the dimension is usually given in inches (2.54 centimeters). The most common dimensions range from 10 to 20 inches.

Load index or load index

Also called load index, abbreviation LI. The load index indicates the load capacity of the tire. A certain load capacity of the tire at a given air pressure of 2.5 bar is assigned to each LI value. Every reduction in tire pressure reduces the load-bearing capacity of the tire.

In addition to the speed index, the load index is an important piece of information that shows the maximum load capacity of the tires. This index itself is a code number that is assigned to a wheel load in kilograms using a table. A detailed load index table can be found under point 2e in the detailed PDF.

The installed tires must at least correspond to the LI specified in the vehicle documents; higher values ​​are permitted. For exceptions to this rule, see point 3 in the detailed PDF.

The air in the tire carries the load. Too little tire pressure can therefore be dangerous, in the worst case the tire will burst due to overheating and mechanical overload. If the air pressure is correct, you are not only safer on the road, but you also save fuel.

The identification of the car tire
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Speed ​​index or speed index

Also called speed symbol, abbreviation GSY. The last letter in this row indicates the maximum speed at which the tires can be driven. The following maximum speeds are assigned to the code letters. The T in our example stands for 190 km / h.

In the case of tires that are approved for speeds of more than 210 km / h (speed index H), the tire load-bearing capacity decreases with the amount of the driven speed above 210 km / h

A detailed speed index table can be found under point f in the detailed PDF.

Directional binding

Mainly on tires with a special profile design. On the side of the tire, there are designations such as rotation, direction of rotation, direction, in combination with an arrow indicating the direction of rotation. This specified direction of rotation or running must be observed when fitting tires.

Individual tire types are marked on the flank with the words "outside" or "out-side". The profiles of these tires are designed in such a way that the tires produce an "unequal" profile pattern for the right and left side when mounted. This is intended by the manufacturers and has no negative effects on the tire properties.

Tubeless / tubeless

Car tires are typically "tubeless" types. Pulling in a hose is not only superfluous, it is - with a few exceptions - not permitted. In the event of a flat tire with loss of air, inserting a tube should only be a temporary stopgap measure. Most of the time this is not even possible.

Winter tires / all-season tires

Anyone who buys winter tires should not only pay attention to quality, individual driving characteristics and the price, but also to the so-called "Alpine" symbol. The three-pointed mountain pictogram with the snowflake in the middle is mandatory for all winter tires manufactured since January 1, 2018.

The previous M + S mark is then no longer sufficient for newly produced winter tires. For a transitional period (until September 30, 2024), however, tires that have already been manufactured with the M + S mark still comply with the winter tire requirement. Consumers do not have to replace their existing winter tires immediately.

A special feature of winter and all-season tires marked with M + S and / or the Alpine pictogram symbol is that their speed index (see above) can be below the maximum design speed (bbH) of the vehicle. Condition: The driver is informed of the reduced maximum speed by a sticker in his field of vision. Alternatively, appropriate settings can also be made in the on-board computer, e.g. speed limiter in combination with information on the display.

Wear indicator

Also called Treadwear Indicator or TWI. The letters "TWI" (or a company logo) are embossed in small letters on the edge of the tread at six points around the tire circumference. At the level of the TWI markings, elevations (ridges) are attached in the base of the main profile grooves. In addition to the individual TWI bars, the profile depth should be measured regularly.

If possible, the tire should not be worn down to a tread depth of 1.6 mm: the grip of some tire models decreases significantly below a tread depth of 3 to 4 millimeters in wet and snowy conditions.

Production date, "DOT number" and "E" approval mark

You can tell when a tire was manufactured on the tire sidewall: The age is usually stamped as a four-digit sequence in the DOT number. The complete DOT number consists of three blocks of four characters each. The third number block is relevant for the date of manufacture. It is usually set off in an oval. The first two digits stand for the week of production, the last two for the year of manufacture. In the picture, the number sequence 0408 means: 4th week of production in 2008.
The fact is: fresh rubber works best. Our investigations with unused new tires have shown that the technical properties can change negatively over the years. New tires should not be older than two years - you can point this out when placing the order.

Read here: How old can a new tire be?

Emergency or run-flat tires

Most of these tires have reinforced sidewalls that the vehicle can support even at low inflation pressures. The speed and driving style must be adapted to the emergency situation.

The vehicle operating instructions provide information on the operating regulations.
So far, emergency tires or run-flat tires (RFT) have been marked on the flank in the same way as standard tires with conventional sidewalls. It is expected that over the next few years tire dimensions will be entered with an RF mark in the registration certificates of individual cars that are fitted with run-flat tires as standard or as an option.

In principle, the vehicle manufacturers and the ADAC already recommend that only run-flat tires be fitted on vehicles designed for run-flat tires, even if standard dimensions are entered in the registration certificates and thus the use of standard tires is permitted.

Further information can be found in the detailed PDF.

Tires for emergency bicycles

Some vehicles are not equipped with fully-fledged spare wheels, but with so-called emergency wheels. In the event of a flat tire, these can be installed in place of the defective wheel as a makeshift solution, e.g. to enable you to continue driving slowly (usually a maximum of 80 km / h) to the next workshop.

Most of the emergency bicycles and their dimensions are not entered in the vehicle documents. For this reason, they may not be used regularly and permanently. The tires on these emergency bikes have dimensions that are similar to those of standard tires, e.g. T 155/70 R 17. The decisive difference is the capital letter "T", which is placed in front of the tire's width. The letter T stands for Temporary use only.

Unless otherwise specified by the vehicle manufacturer, the tires must be inflated with an air pressure of 4.2 bar in order to have the load capacity specified above. Therefore the air pressure of the spare wheel should be checked and adjusted regularly.

Retreaded tires

They are marked with R, retreaded, retreaded or retreaded. The retread date is indicated in the same way as the date of manufacture of completely new tires. Since 2006, only retreaded tires may be sold that have been given an E-mark like completely new tires. It is advisable to only purchase tires with this E-mark.

What deviations between the vehicle registration document and the tires are allowed? See point 3 in the detailed PDF.

The identification of the car tire
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Read here: Information on motorcycle tires

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