ORLANDO, Fla.— Citing safety concerns related primarily to wet braking, AAA Inc. is recommending consumers replace their worn tires at 4/32nds inch tread depth.
Nationwide car owners' club AAA is basing its stance on the results of tests it conducted recently on new and worn tires, which showed significant increases in braking distances in wet conditions as tires wear.
"Tires are what keep a car connected to the road," John Nielsen, AAA's managing director of automotive engineering and repair, said.
"Even the most advanced safety systems rely on a tire's basic ability to maintain traction, and AAA's testing shows that wear has a significant impact on how quickly a vehicle can come to a stop in wet conditions to avoid a crash."
AAA conducted its testing in partnership with the Automobile Club of Southern California's Automotive Research Center. Those tests compared the wet braking performance of new all-season tires and those worn to a tread depth of 4/32nds inch.
According to the tests, tires worn to a tread depth of 4/32nds inch exhibit the following, compared with a new tire:
• An average increased stopping distance at highway speeds of 87 feet for a passenger car and 86 feet for a light truck; and
• A 33-percent reduction in handling ability, for a passenger car and 28 percent for the light truck on average.
AAA's testing involved a Toyota Camry and Ford F-150.
Tires tested on the Camry were: Nexen Classe Premiere CP671; Goodyear Eagle Sport; Fuzion Touring; Pirelli Cinturato All-Season Plus; Kumho Ecsta 4X II; and Michelin Premier A/S.
Tires tested on the Ford F-150 were: Firestone Destination LE II; Bridgestone Dueler H/L Alenza Plus (113T); Cooper Evolution H/T (115T); Michelin Defender LTX M/S (115T); Hankook Dyanpro RH12 (113T); and Goodyear Wrangler Fortitude HT (115T).
The complete results are available on AAA's website.
"AAA's testing demonstrates the impact that tire tread has on safety," Megan McKernan, manager of the Automobile Club of Southern California's Automotive Research Center, said.
"If tested side-by-side at 60 mph, vehicles with worn tires would still be traveling at an alarming 40 mph when reaching the same distance it takes for vehicles with new tires to make a complete stop."
AAA said its research found that tire performance does vary by brand, but price is not necessarily an indicator of quality. Worn tire performance deteriorated significantly for all tires tested, including those at a higher price point.
AAA advises shoppers to research options carefully before selecting a replacement tire for their vehicle, and never choose one based on price alone.
"With newer cars going longer intervals between routine maintenance at automotive service facilities, drivers may not become alerted to the fact their tires are too worn until it's too late," Mr. Nielsen said.
AAA's comprehensive evaluation of tire tread laws and regulations across U.S. states found state requirements range from inadequate to non-existent.
Forty-two states consider 2/32nds inch the minimum legal tread depth. California and Idaho have set the minimum at 1/32nd, while Arkansas, Montana, New Mexico, North Dakota, South Carolina and West Virginia have no legal mininum standards.
The AAA's recommendation is in contrast with Michelin North America Inc.'s contention that removing tires prematurely from service costs consumers billions of dollars and increases the amount of scrap tires to be dealt with.
In response to a query from Tire Business, Michelin offered a prepared response:
"Michelin has begun a conversation about worn tire performance because we believe that consumers should have information about what they can expect from their tires throughout their legal life.
"AAA, like Michelin, is committed to safety, and we are pleased that AAA has added its voice to this topic. AAA's data supports Michelin's position that not all tires are created equal.
"The AAA research also supports our position that as tires wear, their wet stopping ability decreases. We also agree that tire degradation varies significantly among brands and even within brands. In fact, some worn tires perform better than some new tires.
"Wear bars are legally required for all passenger tires sold in the United States. Michelin strongly believes that all tires should be designed to perform to current wear bars, thus resolving safety, financial and environmental concerns.
"We will continue to work to raise awareness on the topic of worn tire testing and look forward to working with industry partners."