Tire Tech

How to Find the Age of a Tire

Locate the letters ‘DOT' (Department of Transportation) on the sidewall; then look for the serial number - a combination of 12 numbers and letters. The last numbers identify the week and year of manufacture. Example: 2608 means 26th week of year 2008.
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P : Designation for a passenger-car tire.
ST : Designation for a trailer tire.
LT : Metric tire designation a light truck tire.
T : Stands for the car's spare, or temporary, tire.
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Tire Ratings
Maximum Speed (mph)
(Note: Light truck tires (LT) are not speed rated. )
Q = 99
S = 112
T = 118
U = 124
H = 130
V = 149
W = 168
Y = 189
Z = Above 149

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Tire Size Designation
The dimensions of a tire are detailed on the sidewall.

In the case of a P215/65R 15 tire above:

P = Passenger car
215 = Width of tire in millimenters
65 = The ratio of the height to the width as a percentage
R = Radial construction
15 = Diameter of the rim in inches.
89 = Load rating per tire

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Tire Load Ranges
Inflation Pressure Assigned For “Maximum Load” Rating

P-Metric (passenger cars)
Standard Load
(SL) = 35 psi

Extra Load
(XL) = 41 psi

Light Truck:

Load Range C
(LRC) = 50 psi

Load Range D
(LRD) = 65 psi

Load Range E
(LRE) = 80 psi

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Light truck size designation using aspect ratio

LT 255/85B16

LT = Light truck tire
255 = Approximate cross section width in millimeters
85 = Aspect ratio (height to width)
B = Bias ply construction (R = Radial construction)
16 = Rim diameter in inches

Light truck size designation using inches

33x12.50R15 LT

33 = Approximate diameter in inches
12.50 = Approximate cross section width in inches
R = Radial construction (B = bias ply construction)
15 = Rim diameter in inches
LT = Light truck tire [b]

Thanks!