Tire maintenance is essential for safe driving, but many drivers routinely drive on tires that are underinflated or badly worn.
That's why the Rubber Manufacturers Association (RMA), a trade group based in Washington, D.C., is sponsoring National Tire Safety Week, June 2 to June 8 2013. The campaign is designed to raise awareness of the dangers of ignoring tire conditions.
"We do it every year," says RMA spokesman Dan Zielinski. "It is a way for the industry to … remind people that taking care of tires is important. It's a year-round job. You need to check your pressure at least every month."
Under normal driving conditions, tires can lose up to 1 to 2 pounds of pressure per square inch (PSI) each month. In addition to reducing the driver's ability to control the car, underinflated tires have an increased risk of overheating, which diminishes tread life and can lead to tire failure.
More than a fourth of all automobiles and about a third of light trucks on U.S. highways have one or more tires that are inflated below the levels recommended by vehicle manufacturers, according to the General Accounting Office (GAO) in 2007.
Best practice for tire maintenance
Under the stress of driving, the rubber of underinflated tires may separate. In a 2012 study, the National Highway Traffic Safety Administration found that cars with seriously underinflated tires were three times more likely to have accidents involving tire failure than other vehicles.
Keith Baumgardner, who reconstructs auto accidents as a forensic tire expert at Tire Consultants Inc. in Alpharetta, Ga, says underinflated tires can cause steering problems that lead to collisions. An underinflated tire is slower to respond when the driver attempts to turn.
Underinflated tires also reach higher temperatures than properly maintained tires, he adds. This can cause failure as materials used to make the tire come apart while the vehicle is in motion.
"The rubber just breaks down and separates," he says. "It will start breaking down at about 200 degrees."
In addition to carefully monitoring tire pressure, drivers need to stay aware of how worn their tires are, Zielinski says.
"Typically, tires last three to four years," he says. "It's based on how much you drive. You see a large number of tires reach their end of life at the three- to four-year mark."
If you drive on tires with badly worn tread, you will have trouble steering and stopping in adverse weather conditions, such as rain, snow and ice, Baumgardner says. Such tires also tend to "hydroplane" on wet roads.
Hydroplaning occurs when a vehicle's tires lift off the road surface. The driver then is unable to properly stop or steer. The grooves of a tire's tread resist hydroplaning by allowing water to flow through them. As they grow worn, they gradually lose their ability to do this. Even a thin layer of water on the highway can cause a vehicle with worn tires to hydroplane.
Kevin Rohlwing, senior vice president of training for the Tire Industry Association, says tires should be replaced once the tread drops below a depth of 2/32 of an inch. Tires with badly worn tread are especially dangerous to drive in wet weather conditions, because of poor traction.
"It's important to keep in mind that as the tread wears down, the stopping ability on wet pavement decreases," he says.
You can measure your tire tread depth by using a penny. Insert the penny into each tire's tread grooves, with Lincoln's head upside down and facing you. If you can see all of Lincoln's head, the depth of the tread is less than 2/32 inch and the tire should be replaced.
When to buy new tires
To extend tire life, drivers should rotate them every 5,000 miles, or as directed by the manufacturer. Rotation is the practice of periodically moving tires from one wheel to another to ensure even tread wear. Rohlwing says it's also important to select a tire dealer who is both knowledgeable and reputable.
Knowledgeable dealers can put you in the proper tires for your vehicle, he says. They also will stand behind their products, replacing tires under manufacturers' warranties if they prove to be faulty. Tire warranties are based on the number of miles the tires are expected to last. If a tire wears out before its estimated mileage limit, it may qualify for replacement.
No matter how well you care for your tires, eventually you will need to replace them. Exposure to air, sunlight, and the elements will cause your tires to gradually wear out, even if you seldom drive, says Baumgardner.
"A lot of manufacturers are recommending complete replacement of the tires after six years, whether they look brand new or not," he says.
5 tips for how to inspect your tires
To keep your tires in peak condition, the RMA recommends that you:
1. Check inflation pressure at least once a month. The proper tire pressure for your vehicle typically can be found on a placard at the edge of the driver's door, on the glove box door, or inside of the trunk lid.
2. Check tires when they are cool, since warm air increases pressure.
3. Don't forget to check the inflation pressure of your spare tire. It won't do you any good if it's flat when you need it.
4. Remember that tire pressure monitoring systems (TPMS) that help motorists detect a loss of inflation pressure are no substitute for checking tires with handheld pressure gauges. Your TPMS warning may come too late to prevent damage caused by underinflation.
5. Make sure your vehicle's wheels are properly aligned. Misalignment can cause uneven and rapid tire wear.