Snow tires have more sipes than summer tires, increasing traction on snow and ice, but reducing grip on dry and wet roads. Tires designed for winter conditions are optimized to drive at temperatures below 7 °C (45 °F).
In much of Scandinavia, Canada, and the US, snow tires may have metal studs to improve grip on packed snow or ice, but such tires are prohibited in certain other jurisdictions because of the damage they cause to the road surface. The metal studs are fabricated by encapsulating a hard pin in a softer material. The pin is often made of tungsten (wolfram) carbide, (hard metal). The softer base is the part that anchors the stud in the rubber of the tire. As the tire wears with use, the softer base wears so that its surface is at about the same level as the rubber, whereas the hard pin wears so that it continues to stick out of the tire. The pin should stick out at least 1 mm for the tire to function properly. Snow tires do not eliminate skidding on ice and snow, but they greatly reduce risks.
Regional symbols and rules
In the United States and Canada, a "3PMSF ("Three Peak Mountain Snow Flake")" symbol means that the tire has exceeded the industry requirement from a reference (non-snow) tire.
In Europe, requirements for snow tires vary by country: in the Austria, Czech Republic, Estonia, Finland, Germany, Latvia, Lithuania, Luxembourg, Poland, Romania, Slovenia and Sweden, the use of snow tires is a legal requirement during winter months (usually November to mid-April) or if snow or slush is present on road surfaces; failure to comply can result in on-the-spot fines from the police. In Norway, drivers of light vehicles (less than 3,500 kg) are required to use winter tires according to conditions, studded tires are not allowed before November 1 unless required by road conditions. Andorra, Italy and Switzerland all recommend snow tires but they are not a requirement.
Snow chains fitted to tires are required in Andorra, Austria, France, Germany, Italy, and Switzerland in certain winter conditions. In Norway, heavy vehicles (3,500 kg or more) are required to bring chains in winter conditions and to use winter tires November 15 to March 31.
Since July 2008, the Czech Republic uses the Europe-wide road sign requiring the use of snow tires in marked mountainous areas during winter. The duration of obligatory snow tire use was originally November – April (Ordinance 208/2008 Sb.). This was later changed to November – March (Ord. 91/2009 Sb.).
Winter/Snow tyre requirements vary significantly across Europe, with different countries having different statutory requirements
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