That wall of numbers and letters on your tire isn't random. Once you know what each block means, you can buy a correct replacement in about thirty seconds and spot a tire that's too old to trust.
The Size Code
Take a common marking like P225/65R17. The P means it's a passenger tire. The 225 is the section width in millimeters. The 65 is the aspect ratio, meaning the sidewall height is 65 percent of that width. The R stands for radial construction, and 17 is the wheel diameter in inches. Match these to what's on your door jamb sticker, not just to what's already mounted, because a previous owner may have fitted the wrong size.
Load Index and Speed Rating
Right after the size you'll see something like 98H. The 98 is the load index; on the standard chart that's roughly 1,653 pounds per tire. The H is the speed rating, good for 130 mph. Going below your original load index is a safety problem, especially on SUVs and loaded minivans.
The Date Code Most People Miss
Look for a four-digit number inside an oval, usually preceded by DOT. A code of 2823 means the tire was built in the 28th week of 2023. Rubber hardens with age even with low tread wear, so most manufacturers suggest replacing tires after six years and not running anything past ten, regardless of how good the tread looks.
Treadwear, Traction and Temperature
- Treadwear: a relative durability number; 400 typically lasts longer than 200, but only compare within one brand.
- Traction: AA, A, B or C, measured on wet pavement, with AA the best.
- Temperature: A, B or C for heat resistance at speed.
Before you pay for a set, check the date codes on the actual tires being installed. Shops sometimes pull older stock from the back, and a tire that sat in a warehouse for three years is already partway through its useful life. A two-minute read of the sidewall protects both your wallet and your stopping distance.