To check tire tread, get a quarter and stick George Washington upside down into the tread. If the tread doesn’t reach Washington’s forehead, it’s time for a new tire. The coin trick is a handy rule of thumb, but for more accurate tread measurement, you can buy a specialized gauge. When the tread dips below the 2/32-inch mark, the tire will be losing performance and it could make for a dangerous drive, especially in the snow.