Tires can lose their footing long before they're worn out. Tests show that tread can give up a significant amount of grip when it's still at the halfway point.
That's particularly worrisome when you realize how many worn tires are on the roads. A recent study by the National Highway Traffic Safety Administration found that nearly 50 percent of the 11,500 cars, pickup trucks, vans, and sport-utility vehicles the agency checked had at least one tire with half-worn tread. Another 10 percent had at least one bald tire.
Worn tires—especially bald ones—can be deadly on wet roads, where the grooves aren't deep enough to channel water out from beneath the tread. The result is hydroplaning, where the tread skims the water's surface and the vehicle no longer responds to the steering wheel. Wet-weather braking and snow traction also decrease as tires wear.
Tires are considered bald when one or more of their grooves reaches 2/32 of an inch deep, compared with about 10/32 of an inch for new tires (tread wear is usually measured in 1/32-inch increments). Manufacturers have made bald tires easier to spot by placing a series of molded horizontal bars at the base of the grooves. The bars become flush with surrounding tread when wear reduces a groove's depth to 2/32 of an inch. That's also the point where tires will flunk a state safety inspection—and where tread must be worn for you to collect on a tire's tread-wear warranty.
Unfortunately, 2/32 of an inch may be too late if you drive in rain .
