Consumer Reports found that even tires with half of their remaining tread intact can still lose their footing, especially in foul-weather. Naturally, tires lose their ability to grip the road in wet weather as the rubber wears away. The lower the thickness of rubber, the more likely they are to lose their footing. However, tests are finding that tread can give up a significant amount of grip even when it’s still at its halfway point.
Half-worn tires can be treacherous on wet roads, as their grooves may not be deep enough to disperse water out from under the tread. The consequence is hydroplaning where the water becomes a barrier between the tire and the road making steering unresponsive. The faster you drive, the greater the risk of hydroplaning, since higher speeds allow less time for water to escape through the tread grooves. During the Consumer Reports testing, half-tread tires began to skim over the water’s surface at as slow as 40 mph, 3-4 mph slower than full-tread tires. Stopping distances also increase making it much harder to stop in emergency or panic situations.
The new study can be worrisome considering the number of worn tires that are on the road. The National Highway Traffic Safety Administration performed a study that found nearly 50 percent of the 11,500 cars, pickup trucks, vans, and sport-utility vehicle the agency checked had at least one tire with half-worn tread. Another 10 percent had at least one bald tire.
Tires are considered worn-out when their grooves reach 2/32 of an inch deep, compared to approximately 10/32 of an inch when new. Manufactures have designed a series of molded horizontal bars at the base of the grooves to indicate that the tread is worn to a minimum. These bars become flush with the tire tread when it’s reduced to the 2/32 of an inch depth.
Based upon the Consumer Reports test results, you may want to consider shopping for new tires when they reach closer to 4/32 of an inch in depth groove.
See the complete article from Consumer Reports at: http://www.consumerreports.org/cro/2012/12/how-safe-are-worn-tires/index.htm#