Traction on snow

Traction is defined as “the ability of a wheel or tyre to hold the ground without sliding”. This is particularly important when surfaces are slippery, like when driving on snow. 

Why is traction important?

Your tyres are responsible for transferring your vehicle’s energy to the road surface and, in the process, moving the car forward. The better the traction, the better the grip.  

Tyre traction is tested and measured on its ability to grip in both dry and wet conditions, as some treads and compounds excel in the dry while others perform better in wet and wintery conditions.

Traction is hardest to maintain in the winter when ice and snow make the road surface slippery and harder to grip.

What affects traction?

Traction is affected by a number of things, including the amount of tyre that’s in contact with the road surface. So, in simplistic terms, a wider tyre has a larger surface area and, in theory, has the greatest traction. But there are other influencing factors such as the tyre’s aspect ratio (the relationship of the width of a tyre to its height), its tread pattern, compound and tyre pressure. 

Plus-sizing tyres (replacing the original tyres and wheels with a wheel that has a larger diameter and a tyre that has a shallower sidewall) affects the aspect ratio and increases the contact surface area. The same can be said of certain tread patterns that have wide surface blocks for greater grip. A softer compound and/or lower tyre pressure will, again, provide more contact. 

What about traction on winter tyres?

Uniroyal’s MS plus 77 (for cars) and SnowMax 2 (for vans/trucks) are designed for winter. Their wide treads with wide, rigid shoulder blocks have additional sipes (narrow grooves) that allow the tyre to grip winter roads while expelling snow build up. 

The MS plus 77 uses a specific silica compound which enables the tyre to interlock with the road surface, giving you more grip, while the SnowMax 2’s V-shaped directional tread pattern gives you more control and better handling on snow and ice.

For optimal safety, we recommend plus-sizing your tyres for winter.

What gives winter tyres their grip?

Winter tyres’ compound contains more natural rubber than other tyres, so they stay flexible when temperatures fall below 7ºC. This rubber has a much lower glass transition temperature than summer or all-season tyres. Glass transition temperature refers to the temperature when a polymer, like a tyre, changes its properties and gets hard and brittle. It’s the reason why plastics left outside in winter crack so easily. So, while other tyres become hard in the cold, winter tyres stay supple resulting in more road contact, less snow build up and more traction.

The softer compound drastically reduces stopping distances while the deeper, narrower tread blocks flex easily to deflect minor imperfections on the road surface, again helping with grip.

What about tread depth and pattern?

Winter tyres, such as Uniroyal MS 77 Plus or Snow Max 2, have deeper tread depths which are designed to allow dry snow to pack into their treads. This packed snow actually helps improve traction and snow-on-snow friction in deep snow.

It all comes down to the fact that the freezing points and melting points of ice are related to both temperature and pressure. If you think of it like a snowball, you can put pressure on the snow and it creates an ice-bond. When a tyre holds a lot of snow, the same thing happens, making it good for traction when a tyre holds a lot of snow in its tread.  

Meanwhile, sipes – tiny channels cut into the tread blocks - allow water, slush and thin snow to be broken up and dispersed. When the tyre rotates these sipes are pressed into the snow. As the tyre flexes, its sipes open up and grab snow and ice, biting them into tiny pieces. 

Uniroyal. A brand of Continental.

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