Modern Tire Dealer

JUN 2018

Magazine for the professional tire industry

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Page 69 of 87

M T D J u n e 2 0 1 8 68 F o c u s o n I n d u s t r y I n 2007, e Tire Rack started a fire storm in the tire industry when it supported a minimum 4/32-inch tread depth. That was in contrast to the generally accepted minimum tread depth standard of 2/32-inch. e results of Tire Rack's own wet trac- tion testing were the basis for its decision to promote removing a tire from service at 4/32-inch. It felt the difference in stopping distance between the two measurements was too dramatic to ignore. It was a safety issue, and remains so, said the company. At the time, Michelin North America Inc. was the only tire manufacturer to respectfully disagree. ere was no data to indicate the 2/32-inch minimum led to an increase in accidents. In addition, there were other factors that favored waiting until 2/32-inch of tread remained (see sidebar, "A costly decision"). e narrative started to change in 2014 when Michelin introduced its Premier A/S passenger tire at the North American International Auto Show in Detroit. Michelin said the main selling feature of the Premier A/S was its ability to retain wet traction as it wears. Suddenly tread depth itself wasn't the focus. Performance, specifically wet traction performance, over the life of the tire was. ree years later, Michelin is pushing for a worn tire testing standard. "Michelin believes all worn tires should be tested," said Andrew Koury, North American brand director for the Michelin brand. "And all drivers need that information. It's critical in the market." JUMP-STARTING THE CONVERSATION Michelin is hosting a global series of events to raise awareness about the importance of worn tire performance in the tire-buying decision. One of the first was a driving event recently held at Michelin's Laurens Proving Grounds in Greenville, S.C. e presentations by Michelin executives always emphasized one message: Worn consumer tires, defined as tires approaching wear out, should be tested. From new to worn, "they change in ways that are simply not clear to consumers at the point of pur- chase," said Eric Bruner, director of external communications. Tom Carter, technical communications director for product marketing, said there are really only three tire components that lead to good wet traction: • an adherent tread compound ("high-grade polymers, high-grade elastomers, high-grade additives, and silica"), • an effective tread pattern ("grooves and edges"), and • a proper contact patch shape. "A rounded contact patch shape will be more efficient in wet than a square simply because you can evacuate water around the contact patch, around the tire." Depending on the tire's design, some worn tires can perform better than some new tires, said Carter. "When you go buy a tire, all the com- pound looks black. You can see the tread pattern, but you can't really see it worn. You can't see the contact patch. at's… why we're trying to start a conversation." BOLD STATEMENT The Michelin Premier A/S is uniquely designed with rain grooves that widen as the tire wears. "Hidden" grooves also emerge over time. e result is a tire the company said continues to evacuate water as the tread depth decreases. Michelin is on record as saying thanks to its new EverGrip technology and a new tread compound featuring "extreme amounts of silica and sunflower oil," the Premier A/S, Bob Ulrich By 'It's critical in the market' MICHELIN CAMPAIGNS FOR WET TRACTION TESTING ON WORN TIRES "Worn tires should be tested and driv- ers should have the information," says Andrew Koury, pictured watching worn tire testing at Michelin's Laurens Prov- ing Grounds in South Carolina. When the tread depth on passenger or light truck tires is worn down to 2/32-inch, Michelin North America Inc. says the tires have reached their legal limit. That's the depth at which Federal Motor Vehicle Safety Standards 571.109 (bias-ply), 571.139 (radial) and, in the case of a vehicle with a gross vehicle weight of more than 10,000 pounds, 571.119 require manufacturers to build/mold in tire tread wear indicators. There is no federal standard that labels 2/32-inch as the minimum allowable tread depth. However, in its 2001 "Everything Rides on It" tire safety campaign, the National Highway Traffic Safety Administration commented on the issue. "In general, tires are not safe and should be replaced when the tread is worn down to 1/16 (2/32) of an inch." Minimum tread depth requirements vary state to state, although 42 states follow the tread wear indicator standard. Two states, including California, have a minimum of 1/32-inch. Six states have no minimum. Continental Tire the Americas LLC recommends tires should be removed from service when the tread depth reaches 4/32-inch — with one exception. Winter tires should be removed at the 5/32-inch mark. Minimum tread depth The definition varies state to state

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