AAA's research appears to contradict Michelin's campaign to convince drivers that they are replacing tires too early.
Driving at highway speeds in wet conditions with relatively worn tires can increase stopping distances by 43 percent, according to a recent AAA study.
The group compared performance using new tires and matching sets worn to 4/32-inch, double the 2/32-inch legal minimum in dozens of states. Stopping distances increased by an average of 87 feet for cars and 86 feet for light trucks, while handling ability was slashed by 33 percent for cars and 28 percent for trucks.
"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," says Southern California AAA research center manager Megan McKernan.
The study appears to contradict Michelin's lobbying campaign against increasing the minimum legal tire tread depth. The company's own study found that some tires can perform as well when worn as new tires on wet roads.
The AAA report suggests tire makers may be pushing to maintain the 2/32-inch replacement guideline in an attempt to minimize warranty costs.