When winter rolls around and the weather turns cold, wet and gray, many motorists have winter tires installed on their vehicle's wheels or have an extra set of wheels with winter tires already installed that can be used in place of the warm weather tires. Because winter tires are used for only a period every year, they may last for years before needing replacement. It's good to know how to determine when winter tires need to be replaced.
Measure the tread depth. How much tread a set of snow tires still has is more important than it is on tires that are used for summer or even all-season use. Because winter tires are designed to be used in snowy conditions, the treads are generally designed to be deeper. And unlike summer tires, which can be driven until the tread is even with the wear marks, winter tires will handle worse if the tread is lower than it should be. For tires driven in wet and rainy conditions, the tread should be no shallower than 1/8 inch. For snowy conditions, tread should be no shallower than 3/16 inch.
Check the manufacture date on the tires. If the tread is still deep enough for effective use in snowy and rainy conditions, then the next thing you can do is determine when the tires were manufactured and whether they are still within their useful life. The DOT (Department of Transportation) requires that tires manufactured since the year 2000 have a number imprinted on the sidewall that has the week of the year and the year it was manufactured in. If the number says DOT U2LL LMLR 5107 for example, the 51 in the last four numbers indicates the week the tire was made (51st week of the year) and the 07 is the year, in this case 2007.
Visually check the tires. Even if the tread is good and the age of the tire still provides safe use, a visual inspection is important. Compare the outside tread to the inside tread to make sure there are no strange wear patterns. Also inspect the tire for bulges and dried or cracked rubber. If you are in doubt about whether your tires are useful, have a professional tire store look at them.
