Winter Tyres

Motoring Weekly is based in Sydney and as such has no need for this type of tyre on its vehicles! What are winter tyres and how do they differ from summer tyres?

For many people in the northern hemisphere, changing tyres is a biannual process – switching tyres to suit the prevailing weather conditions, indeed if anyone in the southern climates of Australia were to go skiing in the Snowy Mountains, then we would certainly recommend them doing the same thing.

Normal road and performance tyres are developed to provide maximum grip on dry tarmac with a tread pattern that can deal with a certain amount of rain – the tread pattern and tyre construction needs to cope with heat, grip and water extraction. They also need to provide as much rubber as possible touching the road surface.

Winter tyres, however, have a different problem to solve: grip in wet or snowy conditions and ambient temperatures far below normal heat cycles for a car tyre. Like a summer tyre, the winter version still needs to get as much rubber connecting with the road surface, however the road may have a layer of snow on it and as such a wider tread pattern is needed to push the softer snow away from the centre of the tyre. Hence the tread pattern would be completely different with larger blocks of rubber and wider channels to push water and soft snow away.

In addition, they need to be able to work in much colder conditions and so the compounds need to be different to cope with a much lower operating temperature. For some areas where snow is inevitable – the northern US states, Canada and much of Northern Europe for example – tyres can be provided with studs to aid traction. This is especially important where roads are snow-bound for months at a time. With regards to compounds, winter tyres often have a higher percentage of natural rubber as opposed to other ingredients that go into a long life road tyre. The natural rubber allows the tyre to retain its soft structure – a normal tyre would start to harden under about 7 degrees centigrade which would affect its ability to provide enough grip. If the tyre is softer then it will be able to flex a little more to get the traction.

The best product to use to gain traction in snow is actually more snow! Subsequently many winter tyres are designed to fill their tread patterns with compacted snow and this helps them on permanently snowed lined roads. It is worth remembering that the grip you get from your vehicle is really the size of your palm at each corner, so it is important to understand how that grip is provided. Some people assume that because they have a four wheel drive or all wheel drive vehicle then they will have more grip in poor conditions. That is not necessarily true. The vehicle’s systems may well help the driver by balancing power delivery, however it is only the tyres that provide grip, so using the wrong tyres in certain conditions will not help!

Image source: rac.co.uk