Car tyres |
2011 |
| A tyre’s contact area with the road is roughly the size of a human palm. Four such contact areas are used to control the vehicle. Grip on the road depends on the quality and condition of the tyre contact area as well as the road surface.
General requirements All vehicles must be equipped with tyres that are in line with the total weight and axis weights of the vehicle. In passenger cars and vans (and special automobiles under 3,500 kg and trailers) the tyres on the same axis must be identical in dimensions, structure and qualities, as well as e, E or DOT approved. Track depth and wearing out |
The development of hydroplaning or slushplaning is affected significantly by driving speed, and also the tyre model, width and especially its condition. Therefore recommended tread depths are: - summer tyre no less than 4 mm and - winter tyre no less than 6 mm The recommended tread depth is therefore double the official minimum requirement. If there is a distinct difference in the condition of the front tyres and rear tyres - but the tyres can still be used - the better pair of tyres should be placed on the rear axis (the car can be either front or rear wheel drive). Air pressure The tyre air pressure must be in accordance with the recommendations of the tyre or vehicle manufacturer. The tyre will wear down rapidly and unevenly, if the air pressure is |
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| incorrect. If air pressure is too high, the tyre gets worn down in the centre; if the pressure is too low, the tyre gets worn on the edges. Correct air pressure affects also the control of the vehicle in a significant way.
Use of winter tyres Winter tyres must be used in December, January and February in passenger cars and vans (and special automobiles with max. total mass 3.5 tons and trailers 750 kg - 3.5 tons). Studded tyres can be used from 1 November to 31 March or the Monday after Easter, the later date being imperative. During other times, studded tyres can be used if the weather conditions require it. Studded tyres are recommended for winter tyres, since the car can be better controlled on icy roads if it has studded tyres. It is prudent to put the studded tyres on the car in due time before the first slippery days arrive. |
All four tyres must be studded tyres in passenger cars or vans (and in special automobiles weighing less than 3,500 kg and trailers). In a trailer with a total mass of 750 - 3,500 kg, studded tyres must be used if the pulling vehicle has studded tyres. The amount of studs in a tyre can be no more than 25 % less than the amount of studs in the tyre with the most studs.
Role of tyres in accidents According to accident investigation boards, 16% (n=543) of the passenger cars and vans which were determined to be the main cause of the accident during 1991-2005 were observed to feature the following tyre-related risks: - worn-down tyres |
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Liikenneturva |
