What Do the Letters in Tires Represent?
2 Answers
Tire specifications are commonly represented by a set of numbers and letters. Taking 235/55-R17-99V as an example, 235 indicates that the tire width is 235mm, 55 represents the aspect ratio of the tire section at 55%, meaning the section height is 55% of the width. 17 denotes the diameter of the corresponding wheel rim, 99 stands for the tire's load index, and V signifies the tire's speed rating. Here is information about tire specifications: 1. Section Width: A wider tire naturally increases the contact area with the ground, which enhances grip and directly improves braking performance. However, there are drawbacks, as more friction surfaces inevitably lead to greater noise and resistance, resulting in increased noise and fuel consumption. Additionally, grip is also related to the tire's material composition. Generally, softer materials provide better grip but reduce durability. 2. Tire Aspect Ratio: An aspect ratio of 55 refers to the ratio of the tire's section height to its section width, with the thickness divided by the width resulting in 55%. This ratio can also be used to deduce the tire's thickness, so a smaller aspect ratio means the tire is thinner.
When I first bought my car, I was completely baffled by the letters on the tires. Later, I realized they weren’t random scribbles but crucial specification details. For example, a common marking like P225/65R17 breaks down as follows: 'P' stands for passenger vehicle tires, '225' is the section width in millimeters, '65' is the aspect ratio percentage, meaning the tire’s height is 65% of its width, 'R' indicates radial construction, which is better suited for modern driving, and '17' is the rim diameter in inches. There are also speed rating letters, such as 'T' for a maximum speed of 190 km/h and 'H' for 210 km/h, which affect high-speed stability. If you accidentally use tires with a lower speed rating for high-speed driving, it could lead to accidents. Load indexes, like '91,' correspond to a maximum load capacity of 615 kg, which is crucial for safely carrying passengers or cargo. I recommend new car owners regularly check these letters on the tire sidewalls to ensure they match the vehicle manual, avoiding the wrong tires that could increase fuel consumption or reduce handling stability. Now, whenever I get in the car, I check the tire markings—it makes me feel like a pro.
