BMW has chosen the Michelin Pilot Sport 4S as a 21in summer tire fitment for its new X3 M and X4 M models. The Competition cars will be fitted with the tire in size 255/40Z R21 102Y at the front and 265/40Z R21 105Y at the rear.
According to Michelin, the Pilot Sport 4S features a number of proprietary technologies, including multi-compound tread patterns and an aramid-reinforced casing design.
The front tires feature Michelin’s tri-compound technology and the rears are bi-compound. Originally developed for endurance race tires, multi-compound technology uses different rubber compounds on different parts of the tread to fine tune the performance.
As an example, the outer shoulder provides exceptional grip and wear resistance in cornering, the intermediate ribs are optimized for steering and handling, and the inner shoulder is designed to break through water and provide grip on wet roads.
When developing the tires, BMW M’s engineers asked Michelin to concentrate on dry performance, grip levels, track endurance and balance on wet surfaces. The fact that the front and rear tire sizes are similar meant Michelin had to engineer the different characteristics with only the tread pattern and the compounds to ensure the design brief was met.
The bespoke versions of the tire took almost three years to develop. Around 800 prototypes were built during this time, and 1,400 pre-production tires were produced and tested at the Nurburgring in Germany, and at test tracks in Miramas and Ladoux, France.