How Pirelli changed winter driving

6d ago

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In October of 1959, Pirelli launched a new tyre at the Turin Motor Show, which would have a huge impact on winter driving.

Back then, as is still the case now, autumn was the time when people started to think about preparing themselves and their cars for the winter season ahead. But they never expected the invention from Pirelli that they were presented with in Turin 60 years ago, called the BS3.

In Italian, this stood for ‘battistrada separata’, or ‘separate tread’. The clue was in the name. This tyre consisted of a carcass and tread pattern as usual, but these were not vulcanised (or ‘cooked’) together, which meant that tread patterns could be switched easily without even removing the wheel from the car.

This allowed the actual tyre to be conveniently adapted for either winter or summer conditions, depending on the season. It was an innovative concept that remained in production for a number of years: foreshadowing the idea of switching tyres for each season.

At the time, nothing like it had ever been seen before in the industry. The man who signed the Pirelli BS3 patent form was an engineer called Carlo Barassi, who at the time was head of technology in Pirelli’s technical office: a department now known as research and development. The actual idea was born a few years earlier: a product of engineer Giuseppe Lugli, who back then was head of the physics laboratory in Pirelli’s tyre department.

Lugli was a great lover of skiing and the mountains, so he was very familiar with the challenges of driving in winter. Up to that point, the best way of dealing with winter conditions for drivers was to strap on snow chains, which simply attach to the outside of the tyre to help provide more grip. But the difficulties associated with that were many and the advantages limited. This technique was something that was actually originally thought of for agricultural vehicles in muddy fields.

How did the BS3 work?

The tread was mounted on three rings of the same diameter as the actual tyre carcass. These were then attached to the tyre carcass and held in place simply by air pressure from the tyre. When the season changed, it was enough to take off the existing tread and replace it with one that was more suited to the weather conditions. The story of the BS3 is also linked to the story of another iconic tyre from Pirelli, as the summer tread pattern for the BS3 was borrowed from the Cinturato.

The arrival of the BS3 ushered in another innovation. Thanks to an agreement with Italian service station chain Autogrill, Pirelli created dedicated workshops on the Autostrada del Sole motorway that links the north of the country to the south. There, Pirelli technicians were able to swap BS3 tread patterns, as well as look after any other tyre-related needs that motorists had.

Pirelli's BS3 also made its presence felt in motorsport. The BS3 was used on the 1961 Rallye Monte-Carlo with excellent results. A total of 28 crews started the rally on this tyre, with 23 of them finishing. Rallying subsequently helped to develop the very first dedicated winter tyre that Pirelli ever released: the MS35.

As for the pioneering BS3, it then evolved into the BS, before the massive strides made in vehicle performance rendered the concept of a separate tyre and tread pattern obsolete.

Pirelli then focused its efforts on pure winter tyres, which brings us right up to the present day. 60 years on, the Italian firm is now able to rely on a specialised family of winter tyres that range from the Scorpion Winter for SUVs all the way to the P Zero Winter for performance cars, as well as the Cinturato Winter for compact and medium cars.

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