How to read your tire spec codes
Your tire size is the long set of letters and numbers printed in raised letters on the side surface of the tire. These numbers are always printed on the OUTSIDE of the tire, the side facing away from the engine. Other codes relating to the manufacturer, place of production, production date, assembly line, and other details are printed on the INSIDE of the tire. On the inside, they can’t be worn off as easily and can provide valuable information in case of a tire related accident or recall. In the example below, the size is P215/65R15 89H where the codes mean…
TireDiagram2.jpg
P- (Vehicle Class)– Tells the intended car type for the tire. “P” is for Passenger cars, “LT” is for Light Trucks, “ST” is for Special Trailers, and “T” means Temporary (The compact spare tire)
215– (Tire Width)– Gives the overall tire tread width in millimeters. (Light Truck tires are measured in inches)
65- (Aspect ratio)– Gives the ratio of the Height (from the rim to the outer diameter of the tire) to the width of the tire. The higher the number, the thicker and the “squishier” the tire, but the smoother the ride is. Lower numbers mean a thinner tire with a rougher ride, but the handling of the car is better.
R– (Construction)– Describes the construction of the tire. “B” for bias belt (Sidewalls and tread are same material, which gives a rigid ride), “D” for diagonal belt, and “R” for radial. If this code is missing, the tire is a cross-ply construction.
15- (Rim diameter)– Diameter of the wheel the tire fits, in inches.
89- (Load rating)– Indicates maximum safe weight for the tire. Ratings range from 60 (551 pounds) to 125 (3,638 pounds). “89” means the tire is rated for 1,279 pounds.
S– (Speed rating)– Tells you the maximum safe sustained speed (not the recommended sustained speed) of the tire. “S“=112mph, “T“=118mph, “U“=124mph, “H“=130mph, “V“=149mph, “Z“=150mph and up.
The other codes aren’t about the tire’s size itself, but information on the strength and durability of the tire. These are the numbers that tell you about the quality of the tire (see the section below called “Knowledge is Power”)
Treadwear– Tells how long the tread should last. This isn’t how many miles it’s rated for, but a tire that has a “220” rating will last about twice as long as one with a “110” rating. Ranges from 110 up.
Traction– How well the tire grips the pavement in wet conditions. Ranges from A (best) to C (worst)
Temperature- How well the tire stands up to heat. Ranges from A (best) to C (worst)
