Even the hottest summer in recorded history will still give way to shorter days, colder nights, and hopefully, snow (at least for those of us above a certain latitude). Many repair shops will start offering deals for tire changeovers so that you can install that staple of winter driving: winter tires. Improvements in tire design and rubber compounds have made all-season tires much more capable, but it’s useful to understand what makes winter tires different and how they can help you maintain control when the mercury drops.
In an attempt to keep you safe no matter what Mother Nature has in store, here’s what sets winter tires apart from your summer cruising rubber.
The rubber that is used in winter tires is designed with very different characteristics in mind. It’s a softer compound and it will retain its flexibility even when the air temperature gets cold, which allows the tire to adjust to changes in the road surface. This is also helped by…
Siping is the process of cutting additional slits into the tread pattern, which improves the ability of the tire to flex. The tread blocks are able to conform as needed and extra points of contact are provided. Siping is undesirable during non-snowy conditions, because it increases wear and tire noise. Audi made a great video explaining how siping works and you can see the siping in the winter tire below.
3. Tread design
Slicks (tires without tread, like those used in racing) provide the optimal level of grip by using a sticky rubber compound and not having any tread. This gives the largest possible contact patch through which the force from the wheels can be applied to the ground. Unlike race cars, street cars need to be able to adapt to changing weather conditions so tread is added to help channel water and snow out from under the tire, thereby allowing the rubber to contact the pavement.
Snow, especially heavy New England snow, presents a challenge as it can plug the channels in the tire. This effectively eliminates the tread and makes it much more likely that the tire will float on the snow rather than cutting through and remaining in contact with the asphalt. Summer tires get clogged especially quickly because they have narrow channels, which are effective at displacing water, but more likely to retain snow. Tread designs on winter tires tend to have larger channels (both wider and deeper) with chunkier tread blocks.
4. Squared shoulders and a narrow tread
Much like your parents probably told you when you were young, winter tires square their shoulders. This, when combined with a slightly narrower tread pattern, is designed to push the tire down through the snow rather than running on top of it. Think of it as the opposite of snowshoes.
For those that live in extremely snowy climates, studded tires are a familiar sight. These tires have metal studs embedded in the tread of the tire. The concept behind them is that the studs will dig into ice and provide traction, much like the claws of a cat. However, the studs are not flexible and the limit the ability of the tread to flex as well, which can limit the grip of the tire under certain snowy conditions. Additionally, studded tires can reduce traction on dry roads because the studs limit the contact of the rubber with the pavement. While it’s a bit dated, here is one video (of many) comparing studded tires with studless tires.
While the studs are designed to dig into ice, it’s not hard to imagine that they will dig into pavement as well: Many states have regulated the use of studded tires to limit the damage to roads. Additionally, studded tires make a fair amount of noise while driving. A Subaru boxer engine with an aftermarket exhaust and studded wheels is practically the state song of Vermont between December to April.
All-season tires, which are equipped on most modern cars when they come from the factory, are designed to function as well as possible across all weather conditions. However, because they have to work in the depths of winter and the summer heat, all while providing good tire life and minimal road noise, they are a compromise. Tire technology has vastly improved over the recent decades, but two specialized sets of tires will usually outperform one set trying to do everything.
When it comes to winter driving, the most useful thing to have in your car is common sense. Tires are getting better, but physics aren’t always friendly. However, this video from Top Gear reminds us that winter driving can be fun under the right circumstances. So get some good tires, be mindful of weather conditions, obey all local laws and ordinances, and enjoy the winter.