How to Read Tire Size Codes?
2 Answers
Tire size codes are printed on the sidewall of the tire. Upon close inspection, you can find numerical sequences similar to the following example. For instance, P215/65R15-89H: 1. "P" stands for Passenger car tire (to distinguish from tires designed for trucks or other vehicle types); "215" indicates the section width of the tire, which is the distance between the two sidewalls (measured in millimeters). This width varies depending on the rim width the tire is matched with: wider rims pair with wider tires, and narrower rims with narrower tires. Generally, the width marked on the sidewall refers to the width when the tire is mounted on a rim of the recommended width. 2. "65" is the aspect ratio, representing the ratio of the tire's height to its width. Here, it means the height is 65% of the width. The smaller the number, the flatter the tire appears; "R" denotes the tire's construction, indicating it's a Radial tire, meaning its cord plies are arranged radially within the tire body. "B" signifies a Bias-ply construction, though bias-ply passenger car tires are no longer in production. 3. "15" indicates the rim diameter (in inches). This tire must be paired with a 15-inch rim; otherwise, it cannot be installed. "89" represents the load index, with this tire's maximum load capacity being 1,279 pounds. Different load indices correspond to different maximum load capacities (usually measured in pounds or kilograms). 4. "H" indicates the speed rating, meaning this tire's maximum speed is 130 miles per hour. In the older European sidewall marking system, it would be denoted as 215/65HR15. Different letters represent different speed ratings.
I usually do my own car repairs, so checking tire models is quite simple for me. You squat next to the car and carefully look at the sidewall of the tire, where a series of numbers and letters are printed, something like '225/55 R17 98H'. Here, 225 is the tire width in millimeters, 55 indicates the height as a percentage of the width, R stands for radial construction, 17 is the rim diameter in inches, 98 is the load index, and H is the speed rating. If you replace tires with a model that doesn’t match the original specifications, it can affect driving stability and safety—I once experienced a situation where the wrong model caused a much bumpier ride. I recommend checking the sidewall when you inspect tire pressure weekly, take a photo of the model and save it on your phone for future tire purchases or emergencies. Regular maintenance can extend tire life, saving both money and hassle.
