The tyre that wore a winter coat
In October of 1959, Pirelli launched an incredible new tyre at the Turin Motor Show, which would change the face of 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 truly innovative tyre consisted of a carcass and tread pattern as usual, but these were not vulcanised (or ‘cooked') together, which meant that the tread pattern could be switched easily, like taking on or putting off a coat.
This allowed the actual tyre to be conveniently adapted for either winter or summer conditions, depending on the season. Furthermore, the switch could be made with very little effort and without the need to take the wheel off the car.
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.
A touch of Italian genius
Nothing like it had ever been seen before in the industry, making this a truly disruptive technology at the time. 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 the unstoppably creative mind of the engineer Giuseppe Lugli, who back then was head of the physics laboratory in Pirelli's tyre department.
Barassi 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: hardly cutting edge stuff.
From service stations to rally stages
Thanks to an agreement with Autogrill, Italy's well-known network of service stations, Pirelli created dedicated workshops on the ‘Autostrada del Sole' motorway that links north to south. There, Pirelli technicians were able to swap BS3 tread patterns, as well as look after any other tyre-related needs that motorists had.
The remarkable innovation that Pirelli introduced with the BS3 also made its presence felt in motorsport: the toughest proving ground of all. The BS3 was used on the 1961 Rally Monte-Carlo with excellent results. A total of 28 crews started the rally on this game-changing tyre, with 23 of them finishing. Rallying subsequently helped to develop the very first dedicated winter tyre that Pirelli ever released: the MS35. Particularly devoted rally fans may even remember the TV adverts for this tyre, with Sandro Munari driving the Lancia Fulvia in which he won several rallies – including the 1972 Monte-Carlo.
In the end, the massive strides made in vehicle performance rendered the concept of a separate tyre and tread pattern obsolete, which finally drew the career of the BS3 to a close. But it was a remarkable story that illustrates the timeless value of thinking outside the box.