What do Tyre Markings Mean?
Buying tyres for the first time many think that tyre markings are complicated. Each tyre has about 20 markings which give complete information about the technical characteristics and performance. Let's figure out the meaning of tyre markings and how to decipher the symbols considering the specific example.
Deciphering tyre markings on the specific example
One of the most important parameters in tyre markings is the size (number 1 in the figure). The size is presented in a universal format - A/B C, where:
- A is the tyre cross section, i.e., width in mm;
- B is the tyre height, indicated as a percentage of the width;
- C is the diameter of the bead ring in inches.
The figure shows a tyre with size 205/55 R16. The marking also includes speed rating and load index as well as other parameters. If you want to read the tyre markings properly pay attention to these characteristics. The main and additional symbols of the tyre markings will be discussed below.
The very first digit in the tyre size (A) is the tyre width. The width of the 205/55 R16 tyre in the figure is 205 mm. The width depends on the features of the vehicle. Many car owners choose tyres with a larger width to make their car look high end.
Height is the next standard parameter in tyre size (B). Marking 205/55 R16 means that the height is 55% of the width. It is easy to calculate: 205 • 55% (0.55) = 112.75 mm.
The larger the B value in the formula, the higher the tyre will be and vice versa. This parameter is very important. So, choosing a tyre with size 215/55 R16 instead of 205/55 R16, remember that the bigger the width, the bigger the height, which is not always appropriate.
The higher wheels could lead to the higher centre of gravity, which impairs the cornering stability of the vehicle and increases the risk of roll-over.
Mounting tyres with a higher profile is advisable for vehicles with stiff suspension to improve driving comfort. It should be noted that the tyre height decreases as the tread wears out during operation.
C in the general formula describes the diameter at rim seat. For the model in the figure, it is 16 inches, which is 40.64 cm (1 inch corresponds to 2.54 cm). The total height of the wheel depends on the diameter of the bead ring and is calculated as the sum of the diameter of the disc and the double height of the tyre. The formula of 205/55 R16 looks as follows:
- The diameter of the bead ring is 40.64 cm.
- Height is 112.75 mm (or 11.275 cm).
- The total height of the wheel is 40.64 + 11.275 2 = 63.19 cm.
What does the Letter R next to the Diameter Mean?
Many believe that the letter R next to the diameter at rim seat means “radius”. But that’s not true at all, since the “R” designation reflects the type of the tyre construction — a tyre with the radial carcass. Most tyres are made with such a cord to ensure better performance characteristics.
This misconception was the reason why persistent expression “tyre radius” appeared. But all it takes to refute this version is to make simple calculations. If R16 would mean “radius of 16 inches”, then what the tyre height would be, when the diameter is 2 radii.
The tyre size is indicated several times in the figure. Below the number 16, there is another additional designation — 91V. The letter designation is a speed rating. The parameter declares the maximum available speed for a particular tyre model. You can find out the corresponding speed value in the table below.
|Speed Rating||Maximum Allowable Speed km/h|
The value of this parameter of car tyres varies from a minimum of 40 km/h (“A”) to 300 km/h (“Z”). The speed rating is assigned to each model after testing on a special stand. The “V” index in 91V marking corresponds to a maximum speed of 240 km/h. The manufacturer recommends the operation speed 10-15% less than the maximum value.
The number 91 in 91V marking indicates the load index. There is a special table to decipher the load index in kilograms or pounds depending on the country of origin. Hence, value 91 corresponds to 615 kg. It shows the maximum permissible load a single wheel can withstand during operating under maximum pressure.
Passenger cars usually have index from 50 to 100, index over 100 is common for truck tyres. The load index is more important for minibuses and trucks. In passenger cars, this parameter is usually extensive; therefore it does not play a decisive role in choosing tyres. But manufacturers do not recommend exceeding the threshold values, as it may lead to deformation of the tyres and accidents on the road.
A trademark or brand is often a basic selection criterion for many drivers. A customer usually relies on the reputation of the manufacturer, own experience and recommendations of friends. The figure shows the tyre of Rosava company. The brand is designated as “Trademark” under number 14.
The model determines the specialization of the tyre. The name is convenient for identifying certain product characteristics. The figure below shows the Rosava ITEGRO tyre. The model is indicated under number 5. In the production of this tyre, rubber compounds from the latest generation rubbers were used, which provided it with confident controllability on both dry and wet roads. This model features also a well-developed tread structure.
Additional Parameters in Tyre Marking
In addition to the basic characteristics, tyre marking includes additional information, such as the production date to evaluate how “fresh” the product is, etc. Information on the type of the product is also applied:
- Tubeless tyres are labeled as TL (TubeLess), see item No. 8 in the figure.
- Tyres with tubes are identified as TT (Tube Type).
The tyre in the figure belongs to the category of tubeless tyres (see number 8, which stands for “tubeless tyre”). Other information you can get from tyre markings:
- 2 — TWI, wear indicator location.
- 3 — hazard warning in case of non-compliance with the manufacturer's recommendations.
- 4 — maximum allowable load and pressure.
- 6 — the number of plies, the type of cord and belt.
- 7 —tyre quality grade according to the US standard.
- 10 — compliance with the US standards.
- 11—date of manufacture.
- 12 —symbol of homologation for compliance with European standards.
- 13 —certificate number for compliance with European standards.
- 15 —manufacturing country, in particular, Ukraine (MADE IN UKRAINE).
- 17 —RADIAL, another designation for radial tyre construction.
Rosava tyres have EU marking with the following key characteristics:
- fuel efficiency (letters A to G, where A is the maximum fuel efficiency);
- wet grip (from A to G, where the first value shows maximum safety);
- noise level (three levels with the last one above the threshold in Europe).
Some models of Rosava tyres may have the marking showing the direction of the wheel rotation (number 9 on the scheme). This allows mounting tyres with a directional pattern correctly.
A thorough understanding of markings is necessary not only for specialists and tyre sellers. Many customers have to deal with tyre markings when buying tyres and the knowledge how to read the information they contain can greatly facilitate the choice of tyres to avoid mistakes.