New tires stop a vehicle on wet pavement 90 feet sooner than worn tires

BOISE – (June 7, 2018) – In some cases, the advice to “tread lightly” can keep you from getting into trouble. But when it comes to driving on wet roads, drivers with worn tires could be in for an unpleasant surprise, according to new research by AAA.

While worn tires are reasonably effective in dry conditions, the safety message is clear – when the weather turns, some drivers will face unexpected danger. Nearly 800,000 crashes occur on wet roads each year, and the lower the tire tread depth, the higher the chances of hydroplaning.

AAA recently tested new all-season tires and those worn to a tread depth of 4/32” to compare their effectiveness in wet conditions. On average, new tires have an improved stopping distance of nearly 90 feet – more than the length of a semi-trailer truck.  When decelerating from 60 to 0 mph, worn tires are still traveling at nearly 40 mph at the point when new tires have already stopped.

Worn tires also exhibit a 33 percent reduction in handling ability for a passenger car, and 28 percent for a light truck.

“Vehicle systems like emergency braking, cruise control, and crash avoidance have become quite advanced, but in wet weather, these features are somewhat neutralized by unreliable tires with inadequate tread,” says AAA Idaho spokesman Matthew Conde. “The area of all four tires in contact with the ground is only the size of a sheet of paper, so when it comes to safe driving on a soggy roadway, high tread depths are needed to wick away moisture and improve handling.”

AAA’s research also compared more expensive all-season tires with less expensive options. On average, the more expensive models did not perform significantly better than the cheaper ones.

“Rather than focus on price, it’s a good idea to research product features and consumer reviews,” Conde said. “That could point you to an effective tire that doesn’t break the bank.”

Due to the decreased performance of worn tires in wet driving conditions, AAA encourages drivers to replace their tires when the tread wear is 4/32” or less. 42 of the 50 states have laws requiring tires to have at least 2/32” of tread, and six states have no tread depth requirements at all.  Idaho and California are the only states that have laws that specifically allow a 1/32” tread depth.

“Idaho’s current law is ill-suited to our driving environment,” Conde said. “With plenty of rain, snow, and ice on Gem State roads at various times of the year, requiring a higher tread depth could prevent some loss of traction issues and may reduce the number of injury and fatality crashes.”


AAA’s tire recommendations

  • Check them monthly. Make sure tires are properly inflated. If you notice any material splitting, have the tire inspected and replaced as needed.
  • Look for uneven wear. Uneven wear can impact braking and handling, and could be a sign of an alignment issue or that tires are over or underinflated.  Rotate tires on a regular basis so that you can make timely adjustments to extend the life of the tire.
  • Do the quarter test. Turn a quarter upside down in the tire groove. If you can see the top of George Washington’s head, it’s time to think about replacing the tire.


“If you begin to lose control of a vehicle on a wet road, reduce speed, and avoid hard braking and sudden turns,” Conde suggested. “Steer in the direction the vehicle should go until you regain control.  During inclement weather, it’s also important to increase your following distance.”

For the testing process, AAA selected the Toyota Camry and the Ford F-150, the most popular vehicles in their respective classes. AAA gathered the study results on a closed course in South Carolina, and they were later validated at a second facility.

“It pays to be forward thinking in matters of vehicle maintenance,” Conde said. “We encourage drivers to never overlook their tires as an important part of safe driving.”