Tires can be an “out of sight, out of mind” component on your vehicle, but worn tires can be hazardous, especially during an unexpected downpour. New research from AAA finds that driving on relatively worn tires at highway speeds and on wet surfaces can increase stopping distances by nearly 90 feet.
That’s more than the length of an eighteen-wheeler.
In partnership with the Automobile Club of Southern California’s Automotive Research Center, AAA conducted testing to understand performance differences at highway speeds between new, all-season tires and those worn to a depth of 4/32″ on wet pavement. The study examined both passenger cars and light trucks.
When the rubber met the road, the passenger car exhibited an average increased stopping distance of 87 feet, versus 86 feet for a light truck. The study also found a 33 percent reduction in handling for a passenger car and 28 percent for a light truck.
“Tires are what keep a car connected to the road,” explained John Nielsen, AAA’s Managing Director of Automotive Engineering and Repair. “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.”
“Traction is your last line of defense,” added Brandon Grade, Service Advisor at Findlay Toyota in Las Vegas, Nevada. “Traction control systems can only do so much when the mechanical grip has been removed.”
By The Numbers
Current industry guidelines and state regulations often recommend tire replacement at 2/32″ depth, if there are any guidelines at all. AAA’s research found such recommendations can vary greatly from state to state. During my time as a Service Advisor, our dealership in South Dakota suggested replacement at 3/32″ but AAA says at 4/32″ stopping performance has already decreased.
And when it comes to wet pavement, the lower the tread depth, the more likely a vehicle will hydroplane.
“AAA’s testing demonstrates the impact that tire tread has on safety,” said Megan McKernan, Manager of the Automobile Club of Southern California’s Automotive Research Center. “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.”
If during a routine oil change, your tires are found to be worn, should you replace them immediately? Budget permitting, yes, but if you cannot that day, it’s best to schedule it as soon as you can.
“I agree that 4/32″ is the time to start paying attention to the handling characteristics of your vehicle and replacement should be at 3/32″ depth,” Grade said. “At that point tires cannot effectively remove water or keep traction.”
“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,” Nielsen warned.
Selecting The Right Tire
While AAA’s research determined tire performance fluctuates by brand, price is not necessarily an indicator of quality, which might come as a relief to some consumers. According to AAA, once worn, performance for all tires tested deteriorated significantly, even those priced higher. AAA says to research tires carefully and never buy one brand based solely on price.
“I disagree with that. Usually higher priced brands are that way for a reason,” Grade explained. “That may be because the tire is meant for a specific use like off-road or racing. The reason for the cost difference is because of the technology put in to the tire.”
Grade also notes that certain vehicles require certain tires.
“Specifically, the Toyota Prius uses tires that are designed to have less rolling resistance,” he said. “I have had customers go elsewhere to get a better price, only to come back complaining about a loss in fuel mileage due to having the wrong tire.”
As for finding the perfect tire, the best route might be to simply get a feel for what others are saying.
“I believe customer reviews are the best,” Grade said. “People will give you real world experience rather than hypothetical, perfect scenario results.”
Tips & Advice
In order to reduce your chances of a collision during rainy weather, AAA recommends reducing your speed and to avoid hard braking and sharp turns. Drivers should also keep their distance between vehicles in front of them and resist the urge to use cruise control in order to respond more quickly if needed. If you start to hydroplane, gently ease off the accelerator and steer in the direction the vehicle should go until traction is regained.
Do not brake forcefully.
There are a few home remedies you can employ too.
“Buy a tread depth gauge, have someone show you how to use it if you need, and keep it in your glove box,” Grade said. “When you check your tire pressures monthly, check the tread depth. Make sure to do it on the outside edge, center, and inside edge.”
If you don’t have a tread depth gauge, grab some loose change.
“Slip an upside-down quarter between your tire grooves and look at Washington’s head – if you can see all of it, it’s time to start shopping for new tires,” Nielsen said.
Carl Anthony is Managing Editor of Automoblog and resides in Detroit, Michigan. He studies mechanical engineering at Wayne State University, serves on the Board of Directors for the Ally Jolie Baldwin Foundation, and is a loyal Detroit Lions fan.