Every time snow season rolls around I get inundated with questions on how effective winter tires really are versus standard, run-of-the-mill all seasons that come factory standard on almost every car you buy these days. Ironically, I get the most questions on this topic from people who have all-wheel-drive cars. The ongoing misconception is that if you have AWD you don’t need to upgrade to winter tires.
How important are snow tires? Well my friend they are so important that in Finland from the first of December to the end of February snow tires are mandatory. I’m thinking the Finns know a thing or two about driving in the snow.
To prove that point we did a comparison between all seasons and winter tires on a rutted snow packed course at Copper Mountain ski resort. Continental Tires graciously sent over a set of their ExtremeContact All season tires and a set of their brand spanking new, highly regarded VikingContact 7 winter tires. The RWD car we wanted to use as a comparison couldn’t make it in time so we did back to back runs in my 600 horsepower AWD Audi RS3 as the test car which will expose a weak tire even in the best of conditions. The differences between the two tires are so stark that it is pretty easily to extrapolate the results.
Here in Colorado AWD cars are ubiquitous. Besides AWD SUVs, which are popular everywhere for some reason I have yet to fathom, Colorado is also one of the top markets for Subaru and Audi, specifically because both brands have built reputations on being bad ass beasts in the snow. AWD seems to be the go to safety net for the huge influx of Californian’s moving into the state a majority of whom have rarely ever seen snow, let alone driven in it.
However, what these people fail to realize is that no matter your drivetrain configuration, the single thing connecting your choice of driven wheels to the ground are those little round pieces of rubber populating all four corners of you car. If those lose traction, then you my friend are what I like to call, well and truly fucked.
Now I feel that the reason that some people have fallen for the AWD fallacy is that they equate the ability of an AWD to accelerate on snow to actual grip. Yes, it is true that all things being equal, an AWD car will accelerate better than a front- or rear-wheel-drive vehicle in most situations. That is due to that fact that an AWD car can use the available traction from all four tires not just two as is the case in FWD or RWD. However, John Q Public then (wrongly) equates that grip he or she feels on acceleration to the overall grip the car has. In this is where things start to go all pear shaped.
The problem with that assumption is that acceleration (and depending on conditions) and a degree of stability under steady state throttle are the only times where an AWD car really has an advantage over any other drivetrain configurations. (Reread that last sentence because it’s real important.)
Basically AWD allows you to get up to speed quickly in winter conditions and feel a bit more confident at speed but once you’re there it offers no additional help. When it comes to cornering or stopping, which arguably are the most important parts of driving (winter or otherwise) AWD has zero advantage over RWD or FWD. In short if you are not on throttle it makes no difference which wheels are driven. Whereas the additional grip of a winter tire will give you better grip in all situations. On throttle or off.
Now that we have debunked the AWD fallacy let’s take a look at the tires themselves and see what makes a winter tire better for winter driving. Depending on where you live, all season tires are just fine a majority of the time. Tire manufacturers design these tires to meet a multitude of design parameters set by car companies. Things like wear, noise, fuel efficiency, and durability all take priority. These are things that average consumers around the country place a premium on for their daily commute regardless of the climate.
Vehicle manufacturers work hand in hand with tire manufacturers to optimize their cars to work with the specific tires provided by the tire guys. That’s not to say you can’t switch tires on your car but that it was optimized to work best with the tires it came with. So vehicle manufacturers have a huge incentive to use a tire that will work well in as many markets as possible. All season tires fit that bill nicely. In fact a better name for them should be all market tires, because they work well enough for every market.
Snow tires on the other hand and made specifically to work well in the snow. Things like noise, handling on dry pavement, and wear all take a back seat to how well the tire works when the white stuff starts falling. Now that’s not to say these tires don’t work well on the pavement, modern snow tires work amazing well in most conditions considering their cold weather focus. But thats a topic for another day. Let’s take a look at how and why these tires offer such a big advantage in the snow.
The three main factors in making a tire work in the snow are rubber compound, tread pattern, and tread design.
Rubber compound is one of the biggest advantages to using a winter tire in cooler climates. All tires have an operating temperature range that they work well in. As all season tires are designed to work well in a wide range of climates they have a pretty wide window of temperatures that they work in. However under about 45 degrees Fahrenheit the rubber compound of the tire starts to harden and the overall grip of the tire decreases. As temps start getting in the single digits the level of grip really starts to drop off a cliff.
Conversely because winter tires have a more focused task they can be designed to work in a narrower range of conditions. To this end winter tires are designed with a special compound of rubber that has the ability to stay soft and pliable even as temperatures drop well below freezing. This allows the tire to better conform to the road surface which keeps a bigger portion of the surface of the tire in contact with the road thereby increasing overall grip.
As with the rubber compound, the tread pattern of an all season tire is once again designed to work in a wide range of conditions and has to conform to meet a wide range of demands. Noise, wet and dry weather handling and fuel economy are all things that take priority over the tires ability to work well in the cold and snow.
When tire engineers are designing an all season tire, they are very limited in what they can do with tread design. Deeper wider treads that can cut through the snow don’t work well in dry warm conditions. The more a tread block can move around and squirm the more heat and noise the tire will generate and because grip is better in dry conditions the load placed on a tire is much higher. The deeper, open tread blocks of a winter tire will deform much easier than the closer tread pattern of an all season tire creating heat and noise. They will also feel far less stable than an all season as the tread moves around under load. However in low grip, winter conditions that same deep, open tread pattern allows the tire to cut through the snow and offers substantially increase grip and stability.
Lastly, tread design has been the battle ground for winter tire manufacturers over the past couple of decades. With new designs seemingly coming out every year. The biggest innovation to winter tread design is sipes. Sipes are small slits in the tires tread block that open up as that section of tire comes in contact with the ground. As they open they remove snow and water from the contact patch of the tire allowing it better bite into the snow surface. Additionally the leading edge for each one of those dozens of sipes digs into the surface of the snow creating additional grip.
The bottom line is when it comes to snowy, icy conditions, a winter tire-shod RWD or FWD car will generally out brake, out handle, and generally outperform an AWD car on all seasons. So, now all you Alaskans can head over to your local dealer and put a deposit down on that GT2RS daily driver you’ve been dreaming about.