All Mud Tires are required to have certain information molded into the side of the tire in a location known as the sidewall. Some of the information is self explanatory while other information requires a little knowledge to decipher. The following will help you understand what this information means.
MUD TIRE Type - This Defines the intended proper use of the tire. P indicates this is a passenger car tire while LT indicates the tire would be for a light truck with a heavier load rating.
MUD TIRE Width - This is the width of the tire measured in millimeters from sidewall to sidewall. An example might be 215 representing 215 millimeters.
Aspect Ratio - This is the the ratio of the height of the tire's cross-section to its width. An example of this might be 65, which means that the height is equal to 65% of the tire's width. To calculate the aspect ratio, multiple the first number (e.g. 215) by the second number with a decimal before the number (e.g. .65). Using the example numbers the tires aspect ratio would calculate as 215x.65=139.75 where 139.75 is the tires height in millimeters. This is the height of the rubber from rim to tread on one side of the tire.
To convert the aspect ratio to a full tire height in inches, do this:
Convert the above calculated tire height (aspect ratio) in millimeters to inches by multiplying the millimeters by .03937 (139.75 x .03937 = 5.5 inches). Then take the inches and multiply by two and add the rim size. Example: 5.5 x 2 + 15 (rim size in inches) = a 26 inch tall tire.
Wheel Diameter - This is the width of the opening in the tire where it would be mounted to a wheel. This is measured from one bead across the opening to the other side of the same bead. This measurement is in inches and an example would be 15 and indicates that this tire is for a 15 inch rim, or wheel.
Load Index - This is a number corresponds to the maximum load in pounds that a tire can support when properly inflated. You will also find the maximum load in pounds and in kilograms molded elsewhere on the tire sidewall.
Speed Rating - This is a number that corresponds to the maximum service speed for a tire. See Chart for ratings. Note: Speed ratings are specific for passenger car tires and not light truck tires. Light truck tires (LT) are not speed rated.
| Rating | Maximum Speed |
| Q | 99 mph |
| S | 112 mph |
| T | 118 mph |
| U | 124 mph |
| H | 130 mph |
| V | 149 mph |
| W | 168 mph |
| Y | 186 mph |
| Z | Above 149 mph |
| Disclaimer for the common sense challenged: Please note that this rating relates only to tire speed capability based on tire tires limits, and is NOT a recommendation to exceed legally posted speed limits; always drive within the legal speed limits. | |
PSI — Pounds per square inch - used to measure air pressure in a tire. The PSI rating on tires is typically the maximum recommended tire pressure for that tire. Tire pressure should always be checked periodically and when the tires are cold. Under normal operation, tires can lose approximately 1 PSI of pressure every month. For every 10 degree change in ambient temperature, tire pressure can change by approximately 1 PSI.
UTQG - This stands for Uniform Tire Quality Grading, which is a quality rating system developed by the Department of Transportation (DOT).
The DOT requires the manufacturers to grade passenger car tires based on three performance factors: tread wear, traction, and temperature resistance. Note: snow tires are exempt from the UTOG rating system.
Tread Wear
| Greater than | 100 | Better |
| 100 | Baseline | |
| Less than | 100 | Poorer |
The tread wear grade is a comparative rating based on the wear rate of the tire when tested under controlled conditions on a specified government test track. A tire graded 200 would wear twice as long on the government test track as one graded 100. Your actual tire mileage depends upon the conditions on which they are used and will vary with driving habits, service practices (alignments, proper air pressure, etc), differences in road characteristics and climate. Note: Tread wear grades are valid only for comparisons within a manufacturer's product line. They are not valid for comparisons between manufacturers.
Traction
| A | Best |
| B | Intermediate |
| C | Acceptable |
Traction grades represent the tire's ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete. The Traction grade is based upon "straight ahead" braking tests; it does not indicate cornering ability.
Temperature
| A | Best |
| B | Intermediate |
| C | Acceptable |
The temperature grades represent the tire's resistance to the generation of heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained high temperatures can cause the materials of the tire to degenerate and thus reduce tire life. Excessive temperatures can lead to tire failure. Federal law requires that all tires meet at least the minimal requirements of Grade C.
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
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