Winter tires for the snow season

You've decided to take the winter tire plunge. Good thinking!

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You’ve decided to take the winter tire plunge. Good thinking!

Any vehicle will have better traction with winter tires, no matter what the road surface.

Now come more questions: “How many tires do I need” and “Which ones are best?”

Question one is a no-brainer. You need four matched winter tires. Every winter tire manufacturer specifies in its fitment guides that winter tires should be put on all four wheels.

Lest you think this is a cash grab, it is not: it is a safety issue. It makes sense when you consider the dynamics of all driving situations.

And whatever you choose for winter, it must carry the Transport Canada/RAC mountain/snowflake logo. Without that symbol on the sidewall, it is not a winter tire. If you see M & S (Mud & Snow) markings on a sidewall, they mean absolutely nothing. There is no standard for this marking; anyone can put it on any tire.

If you’re not convinced you need winter tires on all four wheels, consider the following. If we put them only on the drive wheels, the car will have better traction for going than for stopping or turning. If that car is a FWD, it will be next to impossible to stop without the tail coming around in a panic stop.

Under heavy braking effort, much of the car’s weight is transferred to the front of the car. This makes the rear tires’ contact patch much smaller. As the contact patch shrinks, the rear wheels will likely lock up (stop turning) and when the rear tires lock up, the rear of the car will start to come around and the car will spin — possibly with tragic consequences.

Electronics (ABS) can try to stop this but ABS works by releasing the locked brake. When a locked brake is released, stopping distances increase.

As a general rule, there are few ABS systems that can react quickly enough to stop rear wheel lockup on ice. ABS and stability control systems need time and distance to work. And depending on the brand of the software driving the systems, they need vehicle speed to activate. Some systems do not activate at parking lot speeds.

Consider what happens when we turn into a corner. With two winter tires on the rear only, the rear of the car has more grip and will cause the car to go straight (understeer). If we have two winter tires on the front, the front has more bite and the tail of the car will slew wide (oversteer).

The fact is, for safety we need winter tires on all four corners of the car.

The tire companies will tell you their product is the best under each and every winter travel condition. That is just not the case. There is no one tire from any company that works best on dry snow, wet snow, ice, slush and cold dry pavement. All tire design is a compromise. For every plus in one aspect of tire design, there will be a corresponding minus somewhere else on the performance graph.

The first design choice (and buyer’s choice) is to decide between a high-performance speed-rated tire or an everyday slogger. As a general rule, the lower the speed rating of a winter tire, the more aggressive the tread pattern can be for snow and ice.

The corollary of that rule is: as the speed rating goes down, so does the handling quality of the tire. If you are driving a Toyota Echo, it does not make sense to get a V-speed rated winter tire. If you are driving a BMW 540 that normally runs on V rated tires, you will be seriously underwhelmed by a Q-rated winter tire, unless you regularly drive to Sudbury. If that same 540 spends all its time in the GTA on pavement, an H- or V-rated tire will do the job.

So choose your tire to match your car, your driving and your handling expectations.

The next choice will be conventional design rubber, rubber with additives or multicell compound for the tread rubber. Multicell rubber contains little microscopic air pockets. As the rubber wears, these little pockets are exposed and act like little suction cups to stick to ice.

The Bridgestone Blizzak series of tires and Yokohama’s Ice Guard tires are excellent choices. The downside to this type of tire is quicker wear than conventional rubber and the squishy nature of the tire precludes making it in higher speed ratings.

Tires with additives use grit embedded in the rubber to provide traction on ice. Goodyear uses volcanic sand; Toyo uses ground walnut shells. There is no downside to this technology.

Conventional rubber is just that, high silica content rubber that resists freezing temperatures to provide grip in a broad range of temperatures and conditions. The majority of tire companies prefer using this type of construction and it is the type of tire that is most common.

Here’s where you’ll need your eyes. The tread pattern will tell you what conditions the designers had in mind for the tire.

Open areas in the tire with many jagged leading edges on the tread blocks indicate a tire maximized for snow bite. A tire covered with many little zigzag sipes is designed for ice.

Each tire will also work under other conditions but it will be better in its own field. If a tire has too many sipes and small wiggly tread blocks, it will feel unstable when going in a straight line because the tread will squirm.

Tires with larger shoulder blocks will have better steering response and cornering grip than tires with smaller blocks.;

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