The Incredibly Strange Pirelli BS3 Tire Featured Removable Tread You Could Change Yourself

Normally, tread separating from a tire is a sign that something’s gone catastrophically wrong. Be it due to manufacturing defect, dry rot, or simply heavy wear, tread separation is typically marked by incessant thwapping followed by destroyed quarter panels. But what if tread separation was a feature rather than a defect? Meet the Pirelli BS3, a tire from which the tread was meant to separate for the sake of year-round driving.

Wait a second, what about the BS1 and BS2? Well, they didn’t really exist. The letters in the BS3 alphanumeric stand for battistrada separata, or separate tread, and the 3 stood for the three tread bands. Here’s how the BS3 worked: Tread bands were available in both summer and winter tread patterns and could be slipped on simply by deflating the tire casing. Once the pressure was pumped back up, grooves and air pressure would work to hold the bands to the tire carcass. No adhesives, no bonding through vulcanization, no problem, right?

According to Fondazione Pirelli, this absolutely insane tire was the brainchild of two men: Giuseppe Lugli and Carlo Barassi. See, back when Lugli was in charge of the Pirelli Rubber Sector’s Physics Laboratory, he imagined a tire with separate tread and casing, an idea that never really got off the ground at first. Barassi then refined this concept, starting with a special tire carcass and separating the tread into three bands kept apart by precipitation-evacuating channels. The channels also served two extra purposes; to keep the tread bands in place and allow fitment of tungsten spikes for winter use. Barassi then pinched a summer tread pattern from the Pirelli Cinturato 367, whipped up a winter tread pattern, and unleashed the BS3 at the 1959 Turin Motor Show.

To showcase the effectiveness of the BS3 in slick conditions, Pirelli slapped a set of BS3s on an Alfa Romeo Giulietta and had skaters in really short dresses chase the car around an ice rink. I’m not sure if the skaters’ outfits were necessary for this publicity stunt, but it was Italy in the 1950s so I’ll just roll with it. While this was certainly a neat ad, the real marketing genius came by partnering with the Autogrill network of roadside restaurants and service stations to sell and install BS3 tread bands along the Autostrada del Sole running from Milan to Naples. Presumably, the idea was that owners of BS3 tires could get winter or summer treads swapped on while they had a light snack. Of course, the promotional displays for the BS3 would also alert other motorists of the tires’ presence. Not a bad plan if you ask me.

Pirelli was immensely proud of its BS3 tire, so in addition to print ads, the Italian company took out some airtime to promote this tire innovation. Check out the BS3 spot some two minutes and 33 seconds into the above compilation of ads. While the ad likely provided decent exposure for the tire, I’m not sure what I learned from this advertisement other than to not use a giant flower as an umbrella during wintertime. In fact, it’s worth watching the entire video because it’s absolutely surreal. In addition to the strange visuals, the backing tracks consist almost entirely of slapstick sound effects, creating the ambiance of comedy collapsing in on itself.

[Editor’s Note: Agreed; you should watch that. It’s out there. -DT]

So, did the Pirelli BS3 actually work? Well, yes and no. Motorsport Magazine had a less than stellar experience with BS3 tires during an outing at the Nurburgring. While testing an Auto Union 1000, a band detached from a rear tire, creating a little bit of a situation. The spontaneous mobile tread band evacuation likely caused a great deal of fuss in the Pirelli press office, as a comparison test between the BS3s and Pirelli Extraflex tires was quickly arranged. Not just some parking lot cone work, this comparison test consisted of a tour of Britain and circuit lapping at Oulton park. Bold stuff. While some rubber came detached, the tread bands stayed put, and Motorsport Magazine had some very kind words for the BS3 tires.

[…] but it is significant that each improved his lap times by approx. 5 sec. when using the BS3-shod Oxford. These tyres at first give a feeling of instability, due to their flexible casings, but their superior grip soon becomes evident and corners begin to be taken in impressive drifts. It was particularly noteworthy that whereas the Extraflex screamed loudly as tyres do when tortured in this fashion, the BS3s were uncannily quiet. This silent running is a valuable asset to those who like to hurry round corners and roundabouts without attracting unwelcome attention.

Driving like a nutcase without raising suspicions sounds quite nice, although it sounds like BS3 tires had some very strange handling characteristics. In addition, Pirelli notes that 23 of the 26 BS3-equipped participants in the 1961 Monte Carlo rally finished — a fairly strong showing for the tire. Still, the remote possibility of tread detachment was one that lingered, and the tire’s patented nature meant that imitators didn’t really exist, preventing a wider audience from discovering the joyful weirdness of swappable treads.

In the end, the BS3 was rather short-lived, with production ending in 1964. However, the BS3 spawned a tire much closer to Giuseppe Lugli’s original concept, this time simply called the BS. It may have featured a name that didn’t translate well to English, but it soldiered on until advances in cars and tires consigned detachable treads to the dustbin of history. While we haven’t seen anything like the Pirelli BS3 in decades, it holds a very important place in tire history. Per Pirelli, lessons learned from the BS3 and the subsequent BS were put into practice with Pirelli’s first dedicated winter tire, the MS35.

Not only did Sandro Munari win the 1972 Monte Carlo Rally with a Lancia Fulvia shod with Pirelli MS35 winter tires, Pirelli kept developing winter tires, pushing them to places they’d never been before. Today, Pirelli makes Ice Zero winter tires for icy conditions, Scorpion winter tires for SUVs, and Sottozero winter tires for really fast stuff like the Lamborghini Huracan and the Porsche 911. It’s strange to think that in a way, the very peculiar Pirelli BS3 is partially responsible for being able to truly enjoy Lamborghinis in the snow. That’s not a bad legacy if you ask me.

Lead photo credit: Pirelli