In the fall of 1959, Turin, Italy, staged its 41st Salone dell’Automobile, a major international auto show featuring 65 automakers. The star cars of the show were the Maserati 5000 GT and the Ghia Selene concept.
In addition to car companies, nearly 500 other exhibitors took part, including Italian tire producer Pirelli, which unveiled one of the most unusual automotive products ever mounted on a vehicle.
It was 60 years ago that Pirelli unveiled the BS3 tire. BS was short for battistrada separata, or separate tread.
To make it easier for people to meet legal requirements that winter tires be used in certain locales, Pirelli devised a grooved tire carcass that was vulcanized separately from its tread. The idea was that tread could be switched without removing the wheel from the car, “like taking on or putting off a coat,” Pirelli said in a news release celebrating the tire’s anniversary.
According to the news release, the tire, the BS3, “would change the face of winter driving.”
A customer could purchase a set of BS3 tires, and then revisit a Pirelli service station where the three rings of tread could be changed as needed. The tire would be slightly deflated for the removal of one tread design and its replacement with another. The tire would then be re-inflated, with the tire’s air pressure securing the tread in place.
Remember, this was the era of the bias-ply tire, and they would expand quite a bit — at least an inch in diameter — when pressurized, thus helping to keep the tread rings on the grooved casing.
“It was an innovative concept that remained in production for a number of years,” Pirelli added.
“Nothing like it had ever been seen before in the industry, making this a truly disruptive technology at the time,” Pirelli reported.
The idea is credited to Guiseppe Lugli, an engineer and head of the Pirelli physics laboratory.
“Lugli was a great lover of skiing and the mountains, so he was very familiar with the challenges of driving in winter,” the company said.
Although special winter tires had been developed in the 1930s in Finland, “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 tire to help provide more grip,” Pirelli said.
“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.”
Pirelli noted that the BS3 was responsible for yet another innovation. Pirelli worked with Autogrill, an Italian network of service stations, to create workshops along the Autostrada del Sole, the motorway that runs from the toe of the Italian boot up to the Alps. In these workshops, Pirelli technicians could swap BS3 treads “as well as look after any other tire-related needs that motorists had.”
Pirelli said the BS3 design also was used in motorsports. Nearly 30 of the entrants in the 1961 Monte Carlo Rally used BS3 tires and 23 of them finished.
“Rallying subsequently helped to develop the very first dedicated winter tire that Pirelli ever released: the MS35,” the company said, adding that it’s current range of winter tires includes the Scorpion Winter for SUVs , the Cinturato Winter for compact and mid-size cars, and the P Zero Winter for high-performance cars.