5. Check the sizes and speed/load ratings
Once you've determined the condition of the tires, you'll want to make sure they're right for the car. That means checking that they match the car's required size and have the correct load index and speed rating.
The tire size will be a sequence of numbers and letters, such as P225/60R17. In order, these indicate:
- the type (P for passenger tires)
- the width (225 millimeters)
- the height (60% of the width)
- the construction (R for radial)
- the diameter of the wheel rim (17 inches).
Find the size on each tire's sidewall and check it against the car's required tire size, which you can usually find in the owner’s manual, driver-side door jamb, or gas door. Most cars require the same size tire for all 4 wheels, though a few have a "staggered fitment," with larger wheels in the front or back.
Then check the car's required speed and load ratings. You'll also find these on the tire’s sidewall with a short sequence right after the size, such as 98H. The number is the load index and indicates how much weight the tire can bear, while the letter is the speed rating and specifies the maximum speed the tire can handle.
Make sure both these ratings meet the requirements of the car—exceeding them is OK, but falling short is not. For example, if a car calls for 96U tires, it would be safe to mount 98V tires, but not 89V ones.