When it comes to automobile tires, it is vital to know how to read the sizes to determine the right size and meeting US safety requirements. The following includes the details:

Tire Size Markings

• P = Passenger Car Tire
• LT = light truck tire
• Section Width= Tread- mm)
• Aspect Ratio= 45

This is the aspect ratio of the height of the sidewall to width. This example is 45% of the 245 section that equals 110.25.
 
• Z = Speed Rating
• R =Radial Construction

R is a radial tire. Radial tires contain fabric layers where cords run at right angles to the tire circumference, and additional layers around the circumference strengthen the tread around the circumference. Due to this construction, this tire is the most common automotive tire.
 
• Wheel Diameter (inches)
• Load Index= maximum load-carrying, tire capacity
• W = Maximum Speed Rating

Other Tire Indicators

• U.S. Department of Transportation Markings

Department of Transportation (DOT) number is required for all tires. All tires indicate the tire passes all minimum DOT standards for sale in the US.
 
• Uniform Tire Quality Grading (UTQG) Marking

According to the Department of Transportation, manufacturers must grade tires under the Uniform Tire Quality Grade (UTQG) system. The traction grades are AA, A, B, and C. AA is the highest grade.
?
• Maximum Inflation Pressure and Load

This is the maximum air pressure a tire can hold while operating.

 

Categories: Service