How to Understand Tire Sizes

Tire size terminology is a standardized system used to communicate the specifications of a tire, such as its width, aspect ratio, construction type, and diameter.

By the end of this post, you’ll be able to choose the right tires for your vehicle confidently! Let’s take a look at the example of P215/65R15 89 H tire size and understand it in simple terms.

Tire Type
The first letter in a tire size is the “tire type.” In this example, “P” stands for a passenger car. Other common tire types are “T” for temporary spare tires, “LT” for light trucks, and “ST” for special trailers. In this example, the P: This letter indicates the type of tire. In this case, “P” stands for passenger car tires.

Tire Width
The following number in the tire size is the “width.” This is measured in millimeters, indicating how wide the tire is from sidewall to sidewall. In our example, the width is 215 mm. As a general rule of thumb, wider tires provide better handling and gripping power. In comparison, narrower tires are lighter and can improve fuel economy.

Tire Aspect Ratio
After the width, you’ll see a slash followed by a two-digit number. The “aspect ratio” tells you the tire sidewall’s height as a percentage of the width. In our example, the aspect ratio is 65%. This means that the height of the sidewall is equal to 65% of the tire’s width. So, if our tire width was 215 mm, the height of the sidewall would be 139.75 mm (215mm x 0.65).

Tire Construction
The following letter in the tire size is “R,” which stands for radial construction. This is the most common type of tire construction, and it means that the tire has been designed with radial ply cords.

Wheel Diameter
The last two numbers in the tire size tell you the “wheel diameter.” This is the diameter of the wheel that the tire will be mounted on, and it is measured in inches. In our example, the wheel diameter is 15 inches.

Load Index
A load index is a number that corresponds to the maximum weight that the tire can support. In our example, the load index is 89. The load index ranges from 0 to 279, and the higher the number, the greater the load capacity.

Speed Rating
The speed rating tells the maximum speed the tire can safely travel. The speed rating is represented by a letter ranging from A (the lowest) to Y (the highest). In our example, the speed rating is H, meaning the tire can travel up to 130 mph.

Now that we know all the parts of the tire size, let’s put it all together. The complete tire size for our example would be P215/65R15 89H.

215: This number is the width of the tire in millimeters.

65: This number is the aspect ratio. It represents the height of the tire sidewall as a percentage of the width. In this case, 65% of 215mm is 140mm.

R: This letter indicates the construction type of the tire. “R” means radial construction.

15: This number is the wheel diameter in inches.

89: This number is the load index. A higher number means the tire can carry more weight.

H: This letter is the speed rating. “H” means the tire can be used at speeds up to 130 mph.

Now that you know how to read tire size, you can confidently choose the right tires for your vehicle! Remember these tips, and you’ll be sure to find the perfect tires for your car, truck, or SUV.

That’s all there is to it! Now you know how to read a tire size and understand all the important numbers and letters. This information will come in handy when you’re shopping for new tires. With this knowledge, you can be confident that you’re choosing the right tires for your vehicle. 

Thanks for reading, and be sure to check back soon for more helpful tips and advice! P.S. If you found this article useful, share it with your friends! Help them out and tell them they can come to Tireblogger for all their tire needs. Thanks again!

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