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Tires: all you need to know

The tire is the only part of your car that is in contact with the road. A good choice is tire maintenance is therefore paramount, and yet it is often overlooked.

We tell you everything you need to know about it.

How a tire is made

  1. The tread is the sculpted part in contact with the road. It must be grippy on all types of ground, resist wear and abrasion, heat up slightly, and not put up too much rolling resistance.

  2. The wear indicator consists of bosses located inside the main grooves. It indicates the level of tire wear. Minimum authorized depth: 1.6 mm.

  3. The sidewall is made of flexible rubber, in order to withstand deformations when rolling, to resist and protect the tire from impacts (pavement, pothole, etc.). It therefore acts as a shock absorber.

  4. The carcass ply is made up of textile hoops which go from bead to bead. Each arch forms an angle of 90 ° with the direction of the tire rolling.

  5. The inner sealing rubber is composed of a sheet of very airtight synthetic rubber located inside the tire, it acts as an inner tube (note: automobile tires are called "tubeless", which means they don't have an inner tube).

  6. The beads are used to clamp the tire to the rim and support up to 1800 kg without risk of breakage.

Tire structure

Different types of tires

  • The summer tire: this is the classic tire, designed to run all year round and in all conditions. But as its name suggests, it does not stand the cold well: its optimal performance is around 7 to 8 degrees. By default, these are the tires fitted to new vehicles from most manufacturers.

  • The winter tire: it works well from 6 degrees, and all temperatures are below. At low temperatures, its handling is unmatched. Obviously, it will never achieve the performance of a studded tire, but on snowy and / or icy surfaces, it provides remarkable grip compared to other types of tires.

  • The 4-season tire: it was designed to prevent vehicle owners from having to systematically change tires every year, switching from summer to winter tires, and vice versa. So this is the best compromise between the two previous specifications, but it will never match the performance of either. While it can save you some time and money, it will never be as safe for you as a winter tire during the winter season. Logic.

  • The runflat tire: this is the puncture-proof tire. In the event of a puncture, this allows you to continue driving at a reasonable speed (80 km / h) over a distance estimated between 70 and 100 km. Its reinforced structure allows it not to go crazy. However, not everyone can opt for this type of tire, as it is only suitable for homologated vehicles!

  • “High performance”: Specifically developed for sports cars and ultra-sports cars, this category of tires uses the most sophisticated technologies, benefiting from lessons learned directly from competition. They are designed to accept speeds above 270 km / h. And even if the speed is limited on our roads, they must be able to transmit very significant forces during strong acceleration or extremely powerful braking. They are the subject of very extensive hydraulic studies to evacuate water at high speed on wet roads. They must also provide the best possible compromise between sport, comfort and silence.

  • The "off road": Generally labeled M / T (Mud Terrain) this category is intended for use in difficult conditions. Used by enlightened amateurs for recreation (trial or raiding), they were initially designed for professionals working in difficult, even perilous, conditions. Robust, they benefit from reinforcements and protections to avoid cuts and tears. They have a different “road” and “off-road” distribution according to the models and brands. Their use on the road is limited: because of the large studs, their handling is poorer on asphalt and they are noisier.

  • Light truck / utility tires: They can be recognized by the letter C on their sidewall. They have high load indices suitable for utility vehicles, camper vans and certain heavier minivans which often have a heavy load. These tires sometimes have thicker sidewalls to protect them from friction against sidewalks in urban use. As modern vans are extremely efficient, certain tires have characteristics similar to those of passenger car tires: road holding, comfort, handling, braking. Others, to meet professional uses (construction site approach, agriculture) are developed with more studded profiles. Some manufacturers offer a specific “motorhome” version. The sides are stiffened to limit the balance generated by a higher center of gravity caused by furniture and water reserves.

  • Retreaded tire: Retreading is a technique that increases the life of tires. It consists of replacing the tread of a worn tire with a new tread while keeping the same carcass. This operation is only valid for reusable used tires (PUR).

Advantages and Disadvantages of Low Rise Tires

Tires with less than 25 percent are rarely available on the market. When using such extreme dimensions you have to compromise in comfort. Small bumps in the road will be felt directly and road noise will increase, which affects fuel consumption. Low profile tires are more susceptible to impact or other heavy duty. If the road is in bad condition, the grip of these tires suffers. Of course, low profile tires have - apart from appearance - also advantages. The handling of the curve is better as the stiffness is increased due to the low height. Lateral stability is also good. As with all tires, however, you need to take care of the correct air pressure, because deviations above or below can have unpleasant consequences.

Read tire data

Tire labeling

Tire labeling, compulsory since November 2012, is the result of European tire classification regulations. Tire labeling has a dual purpose:

- improve your safety on the road;

- reduce the environmental impact of road transport.

Three indicators are used and allow the tires to be classified according to:

  • Their fuel efficiency (on a scale from A to G);

  • Their effectiveness in wet conditions (on a scale from A to G);

  • Their sound efficiency (indicated in decibels, on a scale of 3 levels).

Dimensional equivalence

A tire size is considered equivalent to the original size if it complies with the following rules:

Load index (LI: Load Index) strictly equal to or greater than that of the original tire, Theoretical outside diameter (D: Design) included in the tolerance interval of the theoretical diameter of the original dimension. The tolerance interval is defined by +/- 3% of the flange height.

This tolerance is that adopted by the Manufacturers' Organization (ETRTO) which standardizes the dimensional characteristics of tires.

When mounting an equivalent dimension shown in the tables, please especially:

tire / wheel / vehicle compatibility preserving sufficient space (static and dynamic) at the wheel arches.

Tire wear

There are several factors that show that the tire is worn and that should be changed.

Determine the age of a tire

The rubber of the tire, even when it is not in use, has a natural tendency to harden over time and to lose grip quality, with the appearance of fine cracks: it is therefore imperative to know how to determine the age of a tire when it is purchased.

The privileged relationship between and the manufacturers guarantees you tires directly from the factory. The quality of the tires is certified in the same way as with physical dealers.

1 - What is the normal lifespan of a tire?

Manufacturers estimate that the typical lifespan of a tire is between five and ten years at most. This figure will obviously vary depending on the conditions of use or storage of the tire (more or less humid environment, thermal amplitude, etc.). Beyond the five-year mark, consider having all of your tires checked by an approved professional at least once a year. On the tenth anniversary, it will be highly necessary to replace the tire without asking any questions. Obviously the change of a tire is done more on its condition (when its legal limit of wear, puncture.) Than on its age.

2 - Where to see the age of a tire

Modern tires have several mandatory information on their sidewall. In addition to the name of the manufacturer and the size of the model, almost all tires are marked "DOT" (Department of Transportation). The four digits following these three letters correspond to the date of manufacture of the tire. The first two, ranging from 01 to 52, indicate the week in which the tire was produced, while the last two refer to the year. The number "1306" thus informs the user that the tire was designed in the thirteenth week of the year 2006.

3 - The dangers of an overly old tire

Over time, the rubber on the tire hardens, dries out and cracks, which can end up being a real hazard when driving. Hard rubber adheres less easily to the road, especially when the road is wet. Microcracks will also lead to more pressure loss problems. As the rubber is harder, it tends to wear out less quickly, which can mislead the driver as to the actual condition of his tires. If in doubt, it is advisable to have them examined by a professional. "

Visible signs of wear

If your tires are one of those cases of wear, they should be changed.

Some tips

Inflation precautions:

Correct tire inflation is a key factor, not only for optimizing tire performance, but above all for SAFETY. It is necessary to maintain the integrity of the tire, but also ensures good vehicle behavior (road holding, braking).

Only use inflation systems equipped with a pressure limiter and intended for this purpose. In all cases ; no one should remain in the immediate vicinity of the assembly to be assembled. The operator must keep away and out of the trajectories of any projections in the event of an incident.

Working pressure:

The inflation pressure that must be observed is that recommended by the vehicle manufacturer. It can be consulted either:

- on the vehicle itself - door, fuel flap,

- in the vehicle's user manual,

- or failing that in the recommendations of the manufacturers or a guide for the profession.

Under-inflation can significantly affect the behavior of the vehicle. The same is true for excessive over-inflation. (see monitoring and maintenance - pressure).


The consequences of an absence or a lack of balance materialize in particular by vibrations occurring at different speed ranges. Wheel balancing is therefore absolutely essential for driving comfort and maintaining vehicle and tire performance.

Balancing machines must:

- include a centering system compatible with the wheel hub

- be calibrated in accordance with the manufacturers' instructions.

These two points, which determine the quality of the operation and often cause faulty balancing, can result in persistent vibrations.

Fitting new tires at the REAR:

In the case of replacing only two tires, for reasons of safety, grip and handling, it is recommended to fit new tires or those in better condition on the rear axle. This advice is valid for traction or propulsion type vehicles with identical front and rear mounts. The inflation pressures must be readjusted according to the manufacturer's or manufacturer's recommendations. Specific cases: 4-wheel drive vehicles: Just like the manufacturers, and whatever the type of all-wheel drive, we strongly recommend the fitting of 4 identical tires (same size, same range, same article code or CAI (1) and same level of wear); the exception being when the vehicle is originally equipped with front and rear mounts of different dimensions. It is necessary to respect the gap defined by the manufacturer between the developments of the tires of the front axle and those of the rear axle in order to avoid damaging certain elements of the transmission:

- transmission shaft in the case of 4X2 vehicles which can be switched to 4X4,

- central differential, in the case of permanent or semi-permanent 4X4 vehicles. In order to have a uniform level of wear between the tires of the front and rear axles, it is therefore strongly recommended to:

- simultaneously replace the 4 tires.

- periodically, change the two axles in accordance with the manufacturer's recommendations.

If one dimension is replaced by another, a tire of equivalent diameter must be fitted and load indexes and speed symbol equal to or greater than that approved must be observed. It is advisable to call a professional for this operation.

In the event of prolonged parking, do not leave the tires under-inflated, and systematically re-pressurize before any further use.

- also take care to protect the tires from UV rays and to avoid contact of the tires with cold winter soils (concrete, stone, etc.) by placing them on chocks.

Have a professional check the condition of the tread and sidewalls (signs of impact, cracks, cuts, etc.) as well as the condition of the wheels and valves.

Index tables

Tableau d'indices de vitesse

Tableau d'indices de charge


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