What are the differences between a winter tyre and a summer tyre?
A winter tyre is designed to deliver performance below 7°C. It differs from a summer tyre in the flexibility of its rubber at low temperature and by the highly siped tread pattern.
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Very flexible rubber at low temperatures
The properties of the rubber in the tread depend above all on temperature. A summer tyre is optimised to drive at temperatures greater than 7°C. Below this threshold, the rubber in the tread hardens and is less efficient.
In a winter tyre, the elasticity of the rubber shifts towards low temperatures. This guarantees better grip in winter conditions.
A highly siped tread
If you look closely at the tread on a winter tyre, you will see several differencesfrom a summer tyre:
A high notching ratio
The tread pattern on a winter tyre contains several grooves that increase the number of biting edges and attack angles, giving it better traction. Photo Bridgestone Blizzak DMV1
A winter tyre has five times more sipes than a summer tyre. This considerable siping enhances grip by multiplying the number of edges that will interact with the compacted snow on the road.
Photo Dunlop SP Winter Sport 3D
A winter tyre has two, three or four wide central grooves (circumferential) that rapidly evacuate water and slush.
Photo Michelin Primacy Alpin
Often a directional tread…
Winter tyres are often directional, i.e. they take account of the rolling direction. They have a v-shaped design to better evacuate slush and to reduce noise. A directional tyre therefore has an arrow to indicate the direction of rotation.
Photo Goodyear Ultragrip 7+
… and sometimes asymmetrical
Some winter tyres have an asymmetrical tread pattern. The tread is divided into three bands (inner, central, outer), each with different qualities. They work together to optimise the tyre’s performance. The inner and outer portions are called "Inside" and "Outside".
Photo Pirelli WinterSottozero 210