Every tyre carries dozens of numbers, letters and symbols on its sidewall. Yet few technicians can explain without hesitation what exactly each of them means. Meanwhile the correct reading of these data directly influences the safety of the vehicle, the legality of operation and the efficiency of work in the workshop. A wrongly chosen load index or an overlooked DOT code can have serious consequences. This article systematically explains all the key terms and abbreviations you will find on a tyre.
Key findings
| Point | Details |
|---|---|
| Marking on the tyre | Understanding the dimensions and indices is key for the right choice and for safety. |
| The LI and SI indices | An incorrect load or speed index can endanger operation and also the insurance settlement. |
| DOT and age | Always verify the DOT code; ideally use tyres less than 6 years old. |
| Types and markings | Summer, winter and all-season tyres have specific markings (M+S vs. 3PMSF). |
| EU energy label | Classes A-E influence fuel consumption, braking distance and noise. |
What you will find on the sidewall of a tyre: basic terms
The sidewall of a tyre is the manufacturer’s information label. The basic marking consists of the dimension code, the indices and special symbols. For example the marking 205/55 R16 says: tread width 205 mm, profile height 55 % of the width, radial construction (R) and rim diameter 16 inches.
Other important data:
- Load index (LI): the maximum load capacity of one tyre in kilograms.
- Speed index (SI): the maximum permitted speed in km/h.
- DOT code: the date of manufacture (e.g. 2423 = the 24th week of the year 2023).
- 3PMSF (snowflake): certified winter performance.
- XL or REINF: reinforced construction for a higher load.
- TL: a tubeless tyre (Tubeless).
Professional tip: When taking over a vehicle or tyres from the store always check the DOT code first. The age of a tyre cannot be recognised merely by looking at the tread depth.
Dimensions, indices and codes in practice
The load index LI and the speed index SI are binding parameters. The values must never be lower than the vehicle registration document prescribes. For example LI 91 corresponds to 615 kg, while SI V means a limit of 240 km/h.
Here are special abbreviations which technicians often overlook:
- RFT / RF / SSR: Run-flat technology allowing you to continue after a puncture.
- FR / MFS: A protective rim ledge against damage on the kerb.
- C: A tyre for light commercial vehicles (vans).
- LT: The marking for light trucks (Light Truck).
Types of tyres and categories
The basic division is based on the composition of the rubber compound. Summer tyres are optimised for temperatures above 7 °C. Winter tyres have a softer compound and 3PMSF certification. All-season models are a compromise for a mild climate.
| Type | Temperature range | Minimum tread | Certification |
|---|---|---|---|
| Summer | above 7 °C | 1,6 mm | standard |
| Winter | below 7 °C | 4 mm (recommended) | 3PMSF |
| All-season | the whole year | 1,6 mm | M+S or 3PMSF |
Important notice: The marking M+S (Mud and Snow) does not guarantee tested winter performance. Only the symbol of the mountain snowflake (3PMSF) confirms that the tyre has passed a certified test of winter traction.
EU labels and safety
The EU energy label contains three key parameters: rolling resistance (classes A to E, influence on consumption), wet grip (classes A to E, influence on braking distance) and noise in decibels. The difference in braking distance between class A and E on a wet surface can be as much as 5 metres.
Professional tip: For fleets with high mileage invest in class A or B of rolling resistance. With an annual mileage of 30 000 km the fuel saving shows significantly in the operating costs.
Equipment for working with tyres
Knowledge of the terms is the basis, but in the workshop you need equipment which allows you to work precisely. At Kompresory-vzduchotechnika.cz you will find everything for inflation and service.
We offer screw compressors for continuous operation, tyre inflators and complete tool sets. The right air pressure is namely just as important for the life of a tyre as its right choice. Our technical team will help you choose a configuration exactly for your automotive workshop.
Most frequent questions
What exactly do I find out from the DOT code?
The week and year of manufacture. It is recommended to change tyres at the latest after 6 years, even if the tread looks well preserved, because rubber loses its properties over time.
What is the difference between M+S and 3PMSF?
M+S is only a manufacturer’s marking for mud and snow. 3PMSF (the snowflake) is a legally recognised certification for real winter operation.
When must I use a tyre marked XL?
Always when it is stated in the vehicle registration document. XL tyres are designed for higher inflation and a higher total load of the vehicle.
Does the noise level on the label influence the service life?
Not the service life directly, but it influences the comfort of the occupants and the noise pollution of the surroundings. Class A is the quietest choice.