For optimal control of a car, the tyres used must be appropriate for the specific vehicle type, the right size and suited to the road conditions. Worn-down tyres are the most common tyre-related safety risk.
The significance of tyres is particularly high in challenging road conditions. Two out of three accidents related to tyres occur on snowy, icy or wet roads.
Over 90% of the tyre-related risks observed in accident investigations involve worn tyres, tyres that are unsuitable for the weather, or incorrect air pressure.
There are also different types of tyre-related risks seen in isolated cases, such as the tyres spinning in the wrong direction, the wheel studs being too short, or having the wrong kind of rims.
The minimum tread depth of the main tread grooves is 1.6 mm for summer tyres and 3.0 mm for winter tyres.
Summer tyres are considered worn down enough to pose a risk when the tread depth of the most worn tyre is less than 1.6 mm. For winter tyres, even tyres with a still-legal remaining tread depth of 3-5 mm are considered worn down.
While driving speed is the primary cause of a car hydroplaning or slushplaning, the tyres, tyre model, width and condition also have a significant effect. For this reason, the recommended minimum tread depth is 4 mm for summer tyres and 6 mm for winter tyres.
Tyre selection and air pressure
On passenger cars and vans, the tyres on the same axle must have the same dimensions, structure and characteristics. The temporary use of a spare tyre of a different type is permitted.
Tyre air pressure plays a significant role in terms of safety, driving economy and the environment.
Driving on under-pressured tyres
- makes it difficult to control the vehicle in extreme situations,
- makes the car drift to one side and may lead to a tyre blowout,
- increases fuel consumption by 3–6% and
- reduces tyre life span by 25–50%.
Winter tyres may be of either the studded or unstudded variety. The minimum tread depth of the main tread grooves is 3 mm. For difficult road conditions, the recommended minimum tread depth is 6 mm. Winter tyres must be M or MS labelled.
When driving on snowy or slushy roads, the tyre tread pattern and the friction characteristics of the rubber are the main factors affecting traction. In icy conditions, studded tyres provide the best traction.
Winter tyres must be used from December until the end of February.
However, unstudded winter tyres may be used year-round. Studded winter tyres may be used from 1 November to 31 March or until Monday after Easter Monday, whichever comes later. Studded tyres may also be used at other times if required by the road conditions.