Alfa Romeo klub Srbija

Winter tyres
Winter tyres only have to save you from tragedy once to be a worthwhile investment
Text: Malcolm McKay / Photos: Mark Dixon

February 2008

Did you know that below 7˚C, the rubber molecules in your summer-spec tyre treads progressively harden and freeze? This means the tyre is less able to adapt to the contour of the road surface, which in turn reduces grip levels, to such an extent that when braking on a wet – not icy – road from 50mph, summer tyres will need 40 metres to stop, when winter tyres will stop in 34 metres.

It’s a big difference and it’s surprising how few people know that there is such a fall-off in performance of the tyres we normally buy, just because the weather is colder. Of course, the difference on ice and snow is even greater, as the winter tyres’ design cuts through snow and into ice to give a far greater margin of safety than on normal tyres: braking on icy roads from 20mph, summer tyres take 68 metres to stop, while winter tyres will bring you to a halt in 57 metres.

Ideally, tires would all be slicks. Unfortunately, slicks don’t work well in wet weather because they push water ahead of them, creating pools and ultimately hydroplaning (like water skiing on tires if you will, with no directional control whatsoever). Hence, we have grooves designed into our tires, which allows them to channel water away and allow the rubber to maintain contact with the road surface. Performance tires also incorporate softer rubber, or compound, to enhance the grip on the pavement, but typically the higher the performance rating, the faster the tires wear out. Which brings us to winter tires.

Snow tires take the principal of channeling water a step further. Good snow tires use a softer compound than even high performance or all-season tires, allowing them to remain more pliable in freezing temperatures, thus ensuring maximum contact with the road and much better grip on ice. In addition, the tread design allows them to dig into snow and then remove it from the tread area, again optimizing contact with the pavement. Unfortunately, these tires would not last long in warmer temperatures since the temperature of the pavement in the summer would peel the softer compound right off the carcass, so to speak. In a nutshell, that’s why we have winter-only tires.

How many snow tires should be on the average automobile? In the old days, it was normal to only put snow tires on the drive axles. Although considered acceptable at the time since pretty much everything on the road was rear-wheel drive, the difference in tread composition on modern tires, coupled with the different handling characteristics of front-wheel drive cars, which now dominate our roads, makes it imperative to use winter tires on all four corners. Using snow tires only on the front axle of a front-wheel drive vehicle could cause the vehicle to spin out in a panic situation.

Winter driving requires patience, as well as skill and a properly equipped and maintained vehicle to handle the conditions. Think of the other drivers around you when you’re stuck in traffic and remember they’re in the same boat as you. Drive safely and we’ll see you around next spring!

Winter tyres:
Winter tyres are recommended for the period beginning in early November and ending in late March. Wear on winter tyres depends on your vehicle use, the trips you make, and your region's climate. Your winter tyres should always be in excellent condition, because worn winter tyres will be ineffective on snow as well as on wet roads. In order to maintain maximal grip on snow, PNEUS-ONLINE recommends that you mount 4 winter tyres to increase your vehicle's grip during the winter months and that you change these tyres when tread depth falls below 0.13 inches. Finally, you should know that using winter tyres will noticeably affect how your vehicle responds and its roadholding on dry roads.

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