It was at the Turin Motor Show of 1959 that Pirelli launched a pioneering winter tyre: the BS3. The BS stood for battistrada separata, or “separate tread”, because the tread and carcass were not vulcanised together. The idea was that when the first snows began to fall, drivers could simply swap the summer tread for a more grippy winter one without even removing the wheels.
Today, there's no more swapping “separate treads”, but there is an acceptance that winter conditions need different tyre performance to summer; winter tyres now account for more than 30 per cent of European replacement tyre sales, according to figures from the European Tyre and Rubber Manufacturers' Association.
And more than sixty years on, Pirelli continues to build on its experience, introducing innovations from the fields of materials and design development and using modern technologies to lead the market with winter tyres that guarantee the highest levels of traction and stability. Each one is a feat of hi-tech engineering and craftsmanship that makes driving in even the worst winter conditions safer and more enjoyable.
So when are winter tyres needed?
Many people associate winter tyres with snow, but in fact they are designed for the winter season – whenever the temperature drops below 7°C (44.6°F).
They are made of rubber compounds that retain their flexibility in colder conditions and also have tread patterns with optimised grooves designed to displace more snow and water. With European winters becoming warmer and wetter, they need to perform in the wide variety of conditions experienced during a typical winter season.
Why can't you just stick to the same tyres all year round?
The rubber compounds in tyres are polymers that become stiffer as the temperature decreases – and the difference can be significant between the hottest and coldest temperatures. To try to keep the tyre soft – and maintain a good grip on the road – when the temperature drops below 7°C (44.6°F), it is best to use a different formula for this rubber compound.
The way a rubber compound responds to the driving surface is also vital. One that is good on snow, for example, may not respond as well on a dry surface. Or it may lose the ability to dispel water droplets, which means it will not work so well in the wet.
It's perfectly legal to use winter tyres in summer as long as they meet the speed index shown in the vehicle registration document. However, tyres designed to work in higher temperatures will be better for typical summer conditions.
What can tyre engineers do to keep cars safe on the road?
For the compound engineers it is a balancing act. They need to create a softer compound that will give drivers confidence at lower temperatures when it is icy or snowing, which is simple to do by changing the recipe, but they also need to keep enough stiffness in the tyre for when the winter sun comes out and warms the asphalt on the road.
To create the right stiffness at these different temperatures is also complicated by the fact that the stiffness of a tyre is determined by two main factors – the chemistry of the rubber compound and mechanics of the tyre, including the tread pattern.
The tread pattern and rubber compound must work together. A high-quality compound can be very badly affected if it is used with the wrong tread pattern. And the reverse is also true – an excellent tread pattern may not work well or last long if paired with the wrong rubber.
What impact does the tread pattern have?
One of the most important aspects of a tyre is the “land to sea ratio” of the tyre footprint. This describes the amount of rubber in contact with the ground at any one time compared to the space where the grooves are.
A soft slick tyre with no grooves, for example, will behave very differently to the same compound with lots of grooves. In the snow it is more likely to skid and in the wet it can aquaplane. A harder compound with lots of grooves, on the other hand, can deliver force through the footprint even on ice.
There are two main tread patterns for winter tyres: directional and asymmetrical. A tyre with a directional pattern is less likely to aquaplane and has good grip in the snow, making it better for winter conditions. Similarly, an asymmetric pattern handles very well and finds good traction in the wet.
The tread pattern will also affect the durability of a tyre. If it is well-balanced between the centre and the edge of the footprint, as well as between the front and the back, then the level of abrasion will be constant. If there is a good distribution of pressure, then the tyre will last longer.
Do winter tyres really give me the same driving performance in winter as my summer tyres give me in summer?
The winter tyre is transforming the winter driving experience to make driving all through the season a pleasure, as long as you drive carefully, paying attention to the road and climate conditions, which is even more critical in winter than summer. For added peace of mind Pirelli's winter tyres could also feature Run Flat™ and Seal Inside™ technology so you can still drive your car even if you have suffered a puncture. No need to stop on a cold, dark roadside.
All you have to do is choose the right tyre for your car. And as Pirelli co-develops bespoke tyres for the world's best car makers, the ultimate performance is guaranteed every time.
Box story facts
Below Zero
To develop new compounds and tread patterns, Pirelli R&D teams test tyres at temperatures as low as minus 15°C (minus 59°F) in the controlled environment of hi-tech indoor facilities where they can monitor minute differences in performance time and time again. They also use outdoor tracks where temperatures can plummet to minus 30°C (minus 86°F).
3PMSF
The three-peak mountain snowflake (3PMSF) symbol proves that tyres have been put through rigorous tests in winter conditions by a certified external laboratory.
Pirelli winter tyre range
P Zero™ Winter 2
For drivers looking for performance and safety in winter conditions, the P Zero Winter 2 is designed for the highest performance models and has the highest European label classification ('A') for wet grip and excellent snow braking in all sizes.
Cinturato™ Winter 2
Safety and comfort in all winter conditions. Cinturato Winter 2 is the latest product in the completely renewed Cinturato family for modern CAR and CUV vehicles.
Scorpion™ Winter 2
Scorpion Winter 2 is the winter specialist for high performance SUVs. No compromise on safety and performance in winter conditions. Excellent snow performance, excellent wet and aquaplaning performance, low rolling resistance and high efficiency, high mileage and great comfort.
Ice Zero FR™
Whether you are on a special cruise through the frozen countryside or nipping around town to work, rest and play, the versatile Ice Zero FR produces great stability and, thanks to its studless design, amazing driver comfort.
