A Tire That Evolves as It Wears DETROIT - As your tires wear, their ability to maintain grip on wet roads diminishes with reduced tread depth. Michelin has developed a tire that counters the effects of wear with channels that grow wider, and hidden rain grooves that emerge as the tire is used, along with a special rubber compound for wet conditions. Michelin says the tire, the Premier A/S, reduces stopping distances in wet conditions and, when worn, better resists hydroplaning - skating on a thin cushion of water - compared with a conventional tire. The Premier A/S made its debut here on Tuesday at the North American International Auto Show. An all-season touring tire, the Premier is intended for passenger cars like the Cadillac CTS, Ford Fusion and Toyota Camry. The French tiremaker said it was in talks with five automakers to use the Premier A/S as original equipment on some 2015 models. Tires play a crucial role in translating braking force to deceleration, particularly in wet conditions. "Consumers think brakes are the motivating force that stops your car, when in reality tires stop your car," Ron Margadonna, a senior technical marketing manager at Michelin, said in an interview before the show. Michelin's Premier A/S tire with EverGrip technology. Michelin North America The Premier's expanding grooves are found in four channels that run around the circumference and act as the primary means of removing water between the contact patch and the pavement. Existing tires use V-shape channels that become shallower and narrower with wear. But the Premier's grooves are molded so that they are wider at the base of the tread than at the tire's surface. As the tire wears, the surface area of the void increases to partly compensate for its reduced depth. Woody Rogers, a product information specialist with Tire Rack, an online retailer, said he had driven on the Michelin Premier A/S five times and came away impressed. "You have tread with a wide top and a narrow base," he said. That normally would destabilize the tread block significantly, yet as you load the tire for acceleration and cornering and braking, the tread doesn't squirm or wiggle. The shoulders of the Premier A/S also feature more than 150 emerging grooves that, when the tire is new, appear at the surface as narrow sipes. When the tire is a little more than half worn, with roughly an eighth of an inch of tread remaining, the sipes become grooves that measure one-eighth inch in width. The emerging grooves funnel water out from the center of the patch of tire that touches the road. Artists illustrated the tread on Michelin's new Premier A/S tire in low-tech fashion at the Detroit auto show. Goodyear's Assurance TripleTred All-Season has a similar evolving tread pattern with sipes that wear into wider grooves. The key to the emerging and expanding grooves lies in the manufacturing process, though Michelin is coy on the details of how it makes the Premier A/S. Traditional methods would require drawing the tooling through openings that are narrower than the molds, like extracting a clenched fist from a jar of pickles. It is possible that Michelin uses a mold material that is flushed out of the finished tire, similar to sand-casting techniques used for engine blocks. The Premier's increased wet grip is as much a function of its distinctive rubber compound as of its tread pattern. The mixture contains high amounts of silica, a bonding agent that improves wet-weather traction, and sunflower oil, to improve the tire's pliability in colder temperatures. But the new tire isn't a silver bullet. Wet-weather performance will still degrade as the Premier wears and the rain grooves become shallower. Michelin's own data shows that the wet stopping distance from 50 miles per hour increased to 119 feet, from 106 feet, between a new and a half-worn Premier A/S. Still, that increase is less than what is expected from traditional tires. The Premier A/S replaces Michelin's Primacy MXV4 and will be available in the spring starting at $156 a tire. It comes with a 60,000-mile warranty and will be produced in 32 sizes for wheels from 15 to 18 inches in diameter. Later this year Michelin will introduce the Premier LTX, a tire for S.U.V."s and crossovers with the same technologies.