Quarters are safer than pennies when it comes to checking your tires, according to new tests conducted by The Tire Rack, an independent tire tester. With much of the summer travel season remaining and a change of season looming, now is especially important for drivers to be aware of their tires’ condition.
For decades the tire industry has taught drivers to use the so-called penny test as a simple way to tell when tires were worn out. But experts at The Tire Rack say that popular lesson is outdated, compromises safety, and should give way to the quarter test.
In the old penny test, seeing the top of Lincoln’s head while holding a penny upside down in a tire tread groove indicated a tread depth of 2/32-inch (1.6mm) or less, and that the tire needed replacing. Instructions on how to properly check tire tread depth can be found at www.tirerack.com/treaddepth.
In driving tests conducted by The Tire Rack, a late-model pickup truck riding on tires that passed the penny test, legal in most states, averaged 499.5 feet to stop from 70 miles per hour on wet pavement. That’s equal to about 12.5 school busses, or nearly a tenth of a mile.
However, the same vehicle riding on tires that passed Tire Rack’s proposed quarter test stopped almost 122 feet (24%) shorter. These tires had treads measuring 4/32-inch (3.2mm) deep, as measured from the edge of a quarter to the top of Washington’s head. Not only were braking distances significantly reduced, overall grip noticeably improved. Dramatic footage comparing penny- and quarter-tested tires is available online at www.tirerack.com/baldtiredangers
"The penny test was an indirect result of tire warranties," explained John Rastetter, director of tire information at The Tire Rack. "It is to that depth (2/32") that most warranties remain valid, encouraging drivers to drive longer on tires that don’t provide enough wet-weather traction." Tire Rack tests showed that doubling the tread depth at which warranties are voided will improve safety by cutting braking distances and improving traction in the wet. "We know these changes won’t happen overnight so we’re encouraging drivers to pay more attention to their tires now," he said.
Wet/Snowy roads + Worn tires = A real problem
In 2005, 584,000 car crashes occurred in the rain, causing 169,000 injuries and 2,914 fatalities, according to the most current data from the National Traffic Highway Safety Administration (NHTSA). Another 264,000 crashes occurred in snow and sleet, accounting for another 53,773 injuries and deaths.
Rastetter and his team feel many of these incidents were likely related to worn tires since NHTSA data also show some 20 million vehicles have at least one bald tire. In addition, 31% drivers don’t know how to tell if their tires are bald, according to the Rubber Manufacturers Association, a tire industry trade group. A bald tire is one with less than 2/32-inch of tread depth.
Tire companies spend millions of dollars developing tread patterns that channel water away from under a rolling tire. This channeling allows the tire to stay in contact with road surfaces, especially at highway speeds.
As tires wear, their ability to displace water and grip snow is diminished, increasing the chance of hydroplaning. Hydroplaning occurs when tires are forced up off the pavement by water trapped under the tire. The result is a complete loss of traction that leaves drivers helpless to control their vehicles. By the time a tire is near the end of its service life it can displace a tiny fraction of the water, and grip little of the snow, it could when new.
"Riding on worn or bald tires in rain and snow is like trying to ice skate in dress shoes," said Rastetter. "You’re going to lose control."
About The Tire Rack
Founded in 1979, the family-owned Tire Rack has become America’s largest independent tire tester and consumer direct source for tires, wheels and performance accessories. A team of more than 80 test drivers test tires from every major tire manufacturer on a state-of-the-art, 10-acre test facility at the company’s headquarters in South Bend, IN.
Findings are posted free on the company’s website, www.tirerack.com, where consumers can thoroughly research a purchase. The Tire Rack also posts data collected from more than 119,000 consumer surveys representing more than two-billion miles of real-world tire information; the largest known cache of such information anywhere.