Under the skin: Why seasonal tyres will help you get a grip

It's fair to say that the idea of switching to winter tyres hasn’t caught on in the UK to the extent that tyre manufacturers had hoped. But increasing the grip at the tyre contact patch is the best way to maintain the best possible traction and steering on slippery or what engineers call a ‘low-mu’ surface. (The Greek letter µ, pronounced mu, represents the coefficient of friction.)

It might seem that four-wheel drive is a better idea, but it isn’t necessarily. A 4x4 will make the most of the traction available from the four contact patches. It may also help prevent the balance of the car being upset by a clumsy driver stabbing at the throttle.

But if there’s no grip available, the tyres still can’t gain forward traction, stop the car sliding anywhere it wants, or stop it quickly enough under braking, if at all. Four-wheel drive alone can’t prevent any of those things happening and the only thing that can is the grip of the tyres on the road.

In snow, there’s something else to consider: the width of the rubber. Watch any rally video of cars competing in snow and they all have one thing in common: skinny tyres. In snow, whatever the type of tyre, it will get more grip if it can bite down into the surface. Wide tyres, while good for cornering grip in the dry, are likely to fare worse in the snow.

You can probably see where this is heading. A small, front-wheel-drive hatchback with 185-section winter tyres will be more effective in snow than a big 4x4 SUV on fat summer tyres. The winter tyres grip better in snow because they’re designed to, the weight of the engine is directly over the driven wheels even if there are only two, and the tyres are skinny.

It’s not just about snow. Winter tyres have a softer compound that keeps the tread soft and supple in low temperatures, giving more grip on cold, damp or wet Tarmac at anything below 7deg C. That’s due to the chemistry of the compound and the fact that it contains more natural rubber than a summer tyre. Some high-end performance tyres don’t contain any natural rubber at all and can deteriorate and crack over time in extreme low temperatures.

The solid centre band on a high-performance summer tyre designed to give sharp steering response is missing on a winter tyre and there are normally fewer grooves around the circumference than on a summer tyre – depending on the make. However, there are a lot more of those tiny slits in the tread, called sipes. They create more sharp edges to grip the surface as the blocks they define deform in use. In snowy conditions, they also trap the snow, which grips better than wet rubber.

The downside of a winter tyre is that wider fitments especially are likely to be noisier than a summer equivalent, the rolling resistance is higher and the steering response and handling of a performance car in the dry won’t be as good. On a family car with modest performance, though, there’s no reason not to leave them on all year round, dodging the cost and hassle of two sets of tyres and giving much more safety and convenience in the worst winter weather.