Truck tire sizes explained

Published 05-02-2021 Maverik

Truck tire sizes explained

Choosing the right size of the tires of your commercial vehicle or truck or your fleet of commercial trucks is very important. When the size of your tire doesn't go and fit well with the size of the wheel then the ride wouldn’t be very smooth. Affects the safety of the passengers in the truck.

How one should read the size of the tire?

Certain aspects need to be considered while trying to find out the exact size of the tire that needs to be used for your truck. The most important ones are listed below.

Where the size of the tire of the truck is mentioned?

For every single vehicle you own, you will be provided with the user instruction manual. the size of the tires is mentioned in the user instruction manual.  The second important place where it is mentioned is at the door of your car.  The most common method of finding the size of the tire is by looking for the Unique Serial number that is impregnated on the tire of the car.

How to read the unique serial number?

These are the steps you need to follow to read the unique serial number.

Type of tire

The first letter in the series of the number printed on the tire indicates the type. On a general basis, there are two types of tires one being P metric and the other being Euro metric.  The first letter of the unique serial number printed on the tire indicates the subtype of the general P metric size of the tires.  In case there is no single letter that is placed in the first position of the unique serial number then it shows that it does not belong to the P metric category of tires. It instead belongs to the Euro metric categorization of tires. In case you aren't aware of the P metric and the Euro metric categorization, it is recommended to consult an auto spare specialist.

Width of the tire

The first letter printed on the truck tire of the unique serial number is succeeded by three digits. These three digits indicate the width of the tire measured from sidewall to sidewall. The measurement of the width of the tire is in millimeters.

Aspect ratio

The aspect ratio is nothing but the cross-section of the height of the tire to the width of the tire. For instance, if the aspect ratio is given as 165 by 50, it indicates that the height is 50 percent of the width of the tire.


It is vital to understand the material that goes into the construction of the tire. If the letter R is printed on the tire, then it means a radial type of construction, which is from layer to layer. Also, fabric casing is deployed in the radial type of construction. In other types of construction, steel is generally used.


The diameter of the tire is the next digit which is followed after the type of construction. The diameter of the tire is measured from rim to rim.

Load index

The most important detail you need to take note of while choosing the size of the tire is the load index. The capacity of the truck tire to carry loads is one of the significant details. This is followed right after the diameter of the tire.  The term index is used because the load it can carry cannot be represented just by a set of digits. The type of load and the capacity of load can vary and it is represented in the form of range.  There are two types of loads namely standard load and extra load. If the truck tire can only carry standard loads, then the load index alone is mentioned. If the tire can carry extra loads then the load index is followed by the term XL.

Speed rating

There are a certain set of alphabets that denotes the speed the tire can hold and carry forward. For instance, if the letter S indicates the maximum speed the truck tire can withstand and is 100 km/hr, then different speeds are indicated by different speed ratings.

There are other factors as well like temperature rating which indicates the temperature withstanding capacity of the tire when it undergoes friction and other kinds of wear and tear. There are a lot of other factors that need to be zeroed in while choosing the size of the tire. These are the most important ones. Also, do your research before fixing the size of your tire.

Comments (1):

~jadatis 11-02-2021
The title sugests truck tires, but the rest of the story is more about P-tires , is personscar, tires. XL is only used for personscars, and not on trucktires. Trucktires begin at F-load , and also dont have a letter in front of the sises.

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