Tire Replacement

How to Read a Tire Sidewall

Looking to replace your tires? Let's first learn how to decode all those numbers listed on the side of them. Our example below will help guide you through the process.

               

 

                                                                             P215/55R18

Tire Type

In this example, the 'P' stands for passenger vehicle type. Other letters you may see include "LT" standing for light truck, 'ST' standing for special trailer, 'T' standing for temporary, etc.

 

Tire Width

The '215' in this example represents the width of the tire in millimeters. The larger the number, the wider the tire. 

 

Aspect Ratio 

The '55' refers to the sidewall height reflected as a percentage of the width. As such the sidewall height of this tire is 55% of the 215 width. 

 

Construction

The 'R' stands for 'radial' and is the most widely used construction method. Other methods include 'B' which stands for 'belted bias' and 'D' which stands for 'diagonal bias'. 

 

Rim Diameter

In this example, the diameter is '18' inches; thus, the tire will only fit on a 18-inch rim. 

 

Other important information provided on the sidewall of your tire includes:

Load Index and Speed Rating

This indicates the maximum load carrying capacity and top speed a tire is rated for. It is crucial to only install a tire with a load index and speed rating that meets or exceeds your vehicles specifications. 

 

DOT Code

Referred to as the Department of Transportation code, this indicates that the tire has passed all required tests and adheres to a set of safety standards. The tire is then given a set of grouping numbers listed on the tire after the 'DOT'. 

 

UTQG Code

The Uniform Tire Quality Grading (UTQG) system was created by the National Highway Traffic Safety Administration (NHTSA) to test the quality of tires in three main categories:

-tread wear with 100 being the control tire

-traction with AA being the best traction on wet pavement

-temperature with A being most resistant to heat

 

Each tire is given a grade or code. 
 

Maximum Inflation Pressure

This number followed by a 'psi' will indicate the maximum amount

of air pressure the tire can hold. However, you should always set

the tire pressure to the vehicles specifications rather than the tires. 

Now that you are equipped with the information that you need, give us a call today and we can provide you with a quote or other options for replacing your tires!

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McHenry, IL 60050

Tel: (815)385-2266

Morrie & Son's Auto RepAIR

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