Reinhold Deisenhofer says many people are unsure whether they really need winter tires. They might live in a city where it doesn't snow -- and be put off by the cost of a second set of tires. So are winter tires necessary or not?
Bear in mind that the rubber compound in summer tyres begins to harden as soon as temperatures dip close to zero, which can reduce traction considerably. Winter tires stay soft, and offer more grip in cold conditions.
Reinhold says you should switch to winter tires when daytime temperatures drop to seven degrees Celsius. Over 24 hours temperatures can dip considerably below that level, for example early in the morning or late at night. And that affects driving safety. Winter tires are necessary in parts of northern continental Europe, for example, from October through Easter.
You don't need a professional to change tires, by the way. With a good jack and the right tools, you can do it yourself. First, loosen the wheel nuts about a quarter of a turn when the tires are still touching the ground. Then jack up one wheel at a time. While it's in the air, you can remove the wheel nuts and the wheel.
If you drive with summer tires when it's cold, there's not just the risk of skidding.
Your braking distances will also be significantly increased. And not just in wet, snowy or icy conditions.
At low temperatures, you need further to brake with summer tires even when it's dry. It's worse when roads are wet and cold. If you're travelling at 90 kilometers per hour and it's zero degrees Celsius, braking distances increase by 5 meters 40cm - the entire length of a car. When there's snow on the ground, stopping distances increase by 42 meters.
Motor racing fans know that slicks offer maximum traction in dry conditions. But car treads that are worn smooth are dangerous in wet and snowy conditions. If winter tires have less than 4mm tread, their performance is drastically reduced.