New all-season tires last for about six to seven years with minimal use and about three to five years if you drive about 12,000 to 15,000 miles a year. The National Highway Traffic Safety Administration (NHTSA) estimates that worn-out tires cause 11,000 accidents every year. To ensure your safety and others on the road, you must change your tires as and when required. Before you buy them, keep the following points in mind: Know to read the tire codes Learn about the tire code to know the right tire for your automobile. If you look carefully, you will notice a code with letters and numbers on the sidewall of your tire. Knowing the tire codes is important to buy similar or better tires that fit your wheel. Some of the relevant codes you need to know when you buy a new tire are: Tire type – the first alphabets indicate the tire type P for passenger cars LT for light truck tires ST stands for special trailer tires T for temporary or spare tires Tread width The three-digit number represents the tread width, the distance between sidewall edges in millimeters, followed by a slash and a ratio. Aspect ratio A two-digit number follows the slash and indicates the tire height from bead to tread.