When radial tyres were first introduced they came out on millimetric rims in the size 400mm. These were initially 165SR400 tires for the Citroen Traction Avant, which until then had been fitting crossply tyres 140-40 and 150-40 (the 40 being in centimetres rather than the radial tire where it is described as 400mm). Because of the improved grip and longevity of the new 165SR400 radial tires a wide range of car manufacturers started to take advantage and fit them to their new models. Cars such as the Alfa Romeo 1900 and the Lancia Aurelia came out fitted with 165SR400 tires as standard equipment. Ferrari and Aston Martin also had the option of having 400mm Borrani wheels to fit their 250 GT, 250 Tour de France & DB2/4 models with the new 165SR400 radial tires.
When PIRELLI developed their new PIRELLI CINTURATO ™ CA67 tires in the early ‘50s, they immediately developed a 165HR400 tire, being a radial tire developed to compliment the handling characteristics of cars of this period, which did move underneath you. The PIRELLI CINTURATO ™ 165HR400 was a progressive radial tire. Also importantly the PIRELLI CINTURATO ™ 165HR400 CA67 had the higher H Speed rating. Today the PIRELLI CINTURATO ™ CA67 is the only H rated tire in the size 165R400. Manufacturers such as Alfa Romeo continued to fit the CINTURATO ™ 165HR400 CA67 to their 2600 models right through into the late ‘60s. Fortunately PIRELLI continue to manufacture these tires to the highest standards today.