Why do we need another article about XK Jaguar tyres? Surely everything that could be said about tyres for these 1950s sports cars has already been said over the 70 years of their existence – or has it?
Well things change. So hopefully I will be able to shine a little light on these changes.
Dunlop, until 2014, manufactured the 6.00-16 RS5. The RoadSpeed tyre evolved to become the RS5 by 1959 and was fitted to the XK150. Back in the early days of XK racing, the Dunlop Racing option was the R1. Then, in 1958, Dunlop developed the R5 racing tyres. Having recently read Duncan Hamilton’s book Touch Wood he comments on what an improvement the R5 made to directional stability at high speeds.
Jaguar had a long-standing relationship with Dunlop, as a proactive developer of tyre technology – also helped by their location. It is a shame that Dunlop no longer make any historic road tyres. The RS5 is no longer produced. However, the Dunlop Racing 6.00-16 R5 is road legal and has an H speed rating. Avon currently offer a 6.00-16 TurboSpeed crossply tyre, which is a sports car tyre that was often offered as the standard crossply tyre with David Browns Aston Martins, if you didn’t want to upgrade to radial.
There is a selection of alternative tyres out there, but until recently these were the only tyres from a top brand worth considering for a fast car like an XK Jaguar. The recent development in this crossply tyre size has been the reintroduction of Pirelli’s Stella Bianca. In tyre production, no tyre can be the same as it was in the 1940s, because the laws about the materials and compounds used to build tyres has changed. Today’s tread compounds are far cleverer at moving water out of the way and the build quality of a modern tyre factory (especially a company like Pirelli) is far superior to what would be expected in the 1980s, let alone the 1940s. In 2018, Pirelli produced three different carcasses of Stella Bianca and posted them over to the UK. They were followed by a pair of technicians and a test day was set at Blyton.
When finding the best car to test a 6.00-16 crossply tyre, the obvious choice is an XK120 race car. Pretty much most of the top cars of the 1950s fitted 6.00-16 tyres: Maserati A6, 250F, 300S, Ferrari 375 Mexico, 250 GT Europa, Alfa Romeo 1900, Pegaso, Aston Martin DB2, DB2/4, DB MKIII and DB4. Although the Italian cars of this exotic bunch originally fitted 6.00-16 Pirelli Stella Bianca, the
majority of people out there having fun driving around on 6.00-16 tyres today will be doing it in an XK Jaguar of one guise or another. The same reasons that made them sell so well in period are what makes them so much fun today.
Testing completed, a unanimous decision made between the three drivers on the day led to the 6.00-16 Stella Bianca that Pirelli are producing again today. It even qualifies for a V-speed rating, making it capable of enough for anything an XK can throw at it.
XK Jaguar tyres, by Longstone Classic Tyres