Modern street tires have radial grooves—the ones that go around the circumference of the tire—that channel water so the rubber can make solid contact with the road. The more water that can be channeled, the more traction the tires have to do things like turn and stop the car. Typically, these grooves get shallower and less effective as the tire wears, so it takes longer to stop the car on wet roads. When Michelin began looking at designing a new all-purpose tire, it decided improving wet-weather traction on worn tires was the problem to solve.
“That was our mission,” explained Ron Margadonna, senior technical marketing manager for Michelin. “We wanted to change that as much as we could.”
And so the company’s engineers did something very clever and very simple for its new Premier A/S tire: They designed tread grooves that expand as the tire wears, allowing the tire to perform nearly as well when it’s half-worn as it did when new. It’s a novel safety feature with the potential to save lives, and it’s such an obvious idea, we wonder why it took so long to hit the market.
Michelin’s new “Evergrip” tire technology includes three key changes. First, the four radial rain grooves have been redesigned to resemble an inverted V, with a wall angle that results in wider grooves as the tire wears. As the grooves become shallower over time, they retain nearly the same volume. Michelin wouldn’t reveal much about how the tires are actually made, but did say that with a little “tire Pam”, they can pop the tires off their molds during manufacturing—that’s trickier than usual because the tire is actually wrapped around the mold.
The tires also include an “emerging groove” on the shoulder of the tire. Narrow sipes, or tiny carvings on the edge of the tire, help to channel water away from the center of the rubber. On the Premier, these grooves are shaped like teardrops, wide at the bottom and very narrow at the top. As the rubber wears away, the sipes expand into larger grooves appear around half-tread depth, further assisting in wet weather performance by giving a little more room for water to disperse from underneath the tire.
The Premier A/S (all-season) went on sale earlier this year in 32 sizes, covering 70 percent of the market. A recreational pickup/SUV version is coming next year. The company demurred when asked about the Evergrip technology coming to other Michelin tire lines, but said it has the capability to deploy it more widely.
And now, we have evidence that this isn’t just marketing mumbojumbo. Testing by Consumer Reports shows the Premier stops in similar distances on wet and dry roads, both when new and when the tread is worn down to 5/32″, the point where getting new tires is often recommended.
source: wired.com By Jordan Golson