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V. Tires

Chapter 4: Vehicles

Tires are the part of the vehicle in contact with the road.

In addition, the tires must be able to withstand the load and speed of the vehicle without deteriorating.

They must guarantee you maximum reliability, security and performance.

They also help absorb shocks and vibrations and provide a certain comfort.

The tires are designed to be mounted on the wheel rim

They are inflated with a pressurized gas (air or nitrogen)

Tires consist of a radial or diagonal structure.

This structure is located under the tread and helps solidify the tire.

Nowadays, the radial tire  fitted to most vehicles allows you to benefit from: 

  • greater robustness ;
  •  greater longevity ;
  • better workmanship of materials at the tread level ;
  • a reduction in  vehicle energy consumption .


  • Thick layer of rubber in contact with the road surface
  • Hollowed out with sculptures allowing water , snow and dust to evacuate , limits aquaplaning , improves grip and evacuates heat

A tire wear indicator is a small rubber block located on the tread . This is called the Tread Wear Indication TWI. Its thickness limit is set at 1.6 mm for summer tires and 4 mm for a winter tire. When the tread reaches this level, then the tire must be replaced

The markings on the tire

Tires vary depending on the vehicle: 

  • 195: tire width
  • 65: ratio of tire height to tire width
  • R or D: tire structure
  • 15: rim size in inches
  • 95: charging code
  • V: speed code
  • DOT  tire production date , is made up of 4 digits (example 1520: the tire was manufactured on the 15th week of the year 20)

Tire pressure

  • Check regularly when cold (5 km after departure)
  • Perhaps overinflated by 10% for long distance and heavily loaded
  • Never underinflate by 10%
  • Follow the manufacturer’s recommendations
  • A poorly inflated tire reduces the vehicle’s grip, which is dangerous when turning and braking, faster wear , risk of bursting, increased consumption

Change the tire

  • Loosen the bolts  counterclockwise
  • Tighten the bolts clockwise
  • Cross order to respect when mounting it

Winter tires

  • When the temperature drops below 7°C , your tires harden and become less efficient.
  • A snow tire is designed to perform well in extreme winter conditions.
  • Winter tires are marked with the M+S  (Mud and Snow)  symbol.

Studded tires

  • A  studded tire has studs on its tread . This device allows the vehicle to benefit from better grip on a slippery or icy road.

  • Can be placed between November 1 and March 31.
  • Adapt your speed, on a road where the maximum speed is 90 km/h we will do 60 km/h and where it is 120 km/h we will do a maximum of 90 km/h.

Tire chains

  • For driving on snowy roads

  • Used in mountain regions or in exceptional situations.

I test my knowledge with questions

Chapitre 1: La réglementation