There are three separate tread compounds used across the face of the Pilot Sport A/S tread. That solid center rib is actually composed of a narrow strip of a high-grip rubber compound that's reinforced with almost 100-percent silica for exceptional wet traction. "The center section of the tire has about 15 percent of the tread but can affect up to 50 percent of the grip in the wet," explained Osborne.
Just as the center of the tread has a disproportionate effect on wet grip, the tread compounds on the shoulders of the tires largely affect dry cornering-as a car leans into a corner, its suspension tends to load up the outside shoulders of the tires. Using C3M enabled use of a high-grip dry tire compound on the tire's shoulders to enhance dry handling and grip nearly to the level of a summer performance tire. The rest of the tread rubber compound, between the center rib and the shoulder, is comprised of a long-wearing all-season compound that will remain flexible at low temperatures for acceptable grip in winter conditions.
What's UnderneathUnder the tread compound the belt package of the Pilot Sport A/S also reflects the advantages of using the highly flexible C3M process. Ordinary performance tires use a belt package that combines two steel belts overlaid with a longitudinal nylon cap ply. As the tire spins at high speeds, the nylon ply holds the belt edges down, keeping the tire from flying apart.
The new Michelin tire, taking advantage of the precise component placement offered by the innovative manufacturing process, places a longitudinal belt comprised of high-strength Kevlar. On top of this base are placed two conventional angled steel belts, which are then topped at their edges by a two-to-one combination of high-strength Kevlar and flexible nylon. This belt package is highly resistant to tire growth at high speeds, allowing a Z-speed rating (above 150 mph), but it also had an unexpected benefit. The longitudinal Kevlar sub-belt provides enough reinforcement so that the steel belts can be placed at a 33 to 37-degree angle instead of the more typical 22 to 26-degree angle in conventional performance tires. This more open angle allows the tire to envelop bumps and obstacles more readily, improving ride comfort.
Driving The TireMichelin arranged a variety of wet and dry test comparisons at its sprawling Laurens Proving Ground in South Carolina. Comparisons were made to Pirelli and Dunlop all-season performance tires and to a best-selling and highly regarded Goodyear summer performance tire. While it is true that tires developed at a specific company's proving ground always do best at the facility, the Michelin tires were impressive, especially in the amount of grip and control they exhibited on the wet handling course when driven on a BMW 540i.
Likewise, in the dry when fitted to the latest Ford Mustang, the tires were quite impressive, handily outperforming the two all-season competitors and coming close to the Goodyear in overall grip and feel. Remembering that the Goodyear is a true summer tire and claims no winter performance made the Michelins all the more impressive. They only seemed to lack in large-angle turn-in response when pushing the car very hard at its limits.
There was no opportunity to look at the tire's ride comfort or noise character in detail, but neither were any concerns raised in the relatively short test drive. Winter grip was obviously also impossible to assess at the hot South Carolina proving ground.
Technology For A PriceAll of this technology doesn't come cheaply, of course. But the Michelin Pilot Sport A/S will only cost slightly more than the Sport XGT Z4 tire it replaces. Figure on a range between $150 and $275 for a tire depending upon the dimension. All of the 36 sizes of Pilot Sport A/S tires (in diameters from 17 to 20 in. and rim widths from 7.5 to 11 in.) are necessarily built using the C3M process, and all will be built in the United States in two different plants that have been equipped with the technology.
In a world where true tire breakthroughs are rare, the innovative use of a new manufacturing process from Michelin has resulted in an all-season ultra-high-performance tire that seems to eliminate most of the traditional compromises.