Decode Letters and Numbers of Tires to Understand Their Size, Width and Speed Capacity
Is your car not riding smoothly? One reason could be the wrong size of tires. When buying tires for your vehicle, make sure it is made for the make and model of your car. All the information about a tire in the form of letters and numbers is mentioned on its sidewall. With a little explanation, you can decode these letters and numbers. Just learn how to read the code. The numbers on the sidewall indicate the size, type, and performance of the tire.
Here is a quick explanation about reading each number or letter.
Let’s use this number of a tire as an example: P215/65R15 95H

Tire Type

To understand tire type, you need to decode letters “P” and “LT”
For most vehicles, you can see the letter ‘P’ before the number sequence begins: P215/65R15 95H
Letter ‘P’ stands for ‘P-metric’. It is a designation by the Tire and Rim Association for a ‘passenger car’ tire type. Therefore, the letter ‘P’ signifies that the tire has been designed for passenger vehicles, such as cars, SUVs, minivans, and other light-duty pickup trucks.
If you see ‘LT’s instead of ‘P’ it means the tire has been manufactured for ‘light trucks.’ LT is short for ‘LT-metric.’ It is a designation by the Tire and Rim Association for a ‘light truck’ type tire. Light truck tires are made to be used on vehicles capable of carrying heavy cargo or pulling trailers.
Likewise, ‘ST’ stands for ‘special trailer’ and ‘T’ means ‘temporary’ for your spare tire.

Tire Width

The tire size we have chosen is P215/65R15 95H.
The first number that appears on the tire sidewall is the width in millimetres i.e. mm. In general, the width of a tire is the measurement from one sidewall to another. A tire with ‘P215’ is for passenger vehicles. This tire has a nominal width of 215 mm.

Aspect Ratio

Aspect Ratio is the ratio of the tire's cross-section height to its width.
It is delivered in percentages. After the slash mark, the next number you see signifies the aspect ratio of the tire.
So, the ‘65R15’ from the tire number P215/65R15 95H tells you how tall your tire’s profile is.
Tire manufacturers calculate the aspect ratio by dividing a tire’s height off the rim by its width.
In our example, 65 means that the height is equal to 65% of the tire's width.


A letter after the aspect ratio shows the type of internal construction maintenance of your tire stability. It tells how tire layers were put together.
Please note that there are two types of construction that you may see. First is ‘R – Radial’ and second is ‘D – Diagonal or B -Bias Ply.
The letter ‘R’ means Radial. It refers to layers run radially across the tire. "B" stands for bias construction. It means the layers run diagonally across the tire.

Rim Diameter

The next number is the diameter code, in inches or cm of the wheel from one end to the other. This number is the diameter code of the rim onto which the tire can be mounted. For instance, a tire with the P215/65R15 95H would fit a rim with a 15-inch diameter. So, it is always wise to replace a tire on a rim with another tire of exactly the same rim diameter designation and suffix letters.
When viewing a tire sale in Toronto, you will happen to see many Common Diameter Sizes: 14-Inch Diameter, 15-Inch Diameter, 17-Inch Diameter, 18-Inch Diameter, 19-Inch Diameter, 20-Inch Diameter and so on.

Load Index

Load is a number that indicates the load capacity. The next figure in the sequence corresponds to how much weight the tire can support when fully inflated. Most of the passenger car tires load indexes range between 75 and 100. It is called load index because the number does indicate the specific amount of weight the tire can carry.

Speed Rating

The final figure in the sequence of tire size is the speed rating. It is displayed by a letter: P215/65R15 95H. It tells the maximum service speed for a tire. A speed rating does not indicate how well a tire handles or corners. It corresponds to a particular speed capability based on a standardized laboratory test.
Limitless Tires is a popular rim and tire shop in Toronto. Get services related to rims for sale in Toronto, tire installation, custom wheel visualization, wheel alignment and wheel balancing. Contact us to choose your tire size, determine the right width, and get assistance for tire financing.