Tire Basics


Key Points For Proper Tire Maintenance - Check tire pressure regularly - Rotate the tires every 6,000 - 8,000 miles - Have the wheels alignment checked every two years or if you suspect the suspension has been damaged - Have the wheels balanced when the tires are new and again if you notice a "shimmy" in the steering wheel - Check for advanced and unusual wear which can reduce the ability of tread to grip the road in adverse conditions. Visually check your tires for uneven wear, looking for high and low areas or unusually smooth areas. Also check for signs of damage. Passenger Tire Sidewall Information Example: P225/50R16 92V "P" means this is a passenger car tire (as opposed to a tire made for a truck or other vehicle). P-metric is the U.S. version of a metric tire-sizing system. "225" Section Width: The width of the tire in millimeters from sidewall to sidewall. This measurement varies depending on the width of the rim to which the tire is fitted: larger on a wider rim, smaller on a narrow rim. The number on the side of tire indicates the width measured with the tire fitted to the recommended rim width. "50" Aspect Ratio: The ratio of height to width; this tire's height is 50% of its width. "R" Construction: How the plies are constructed in the tire carcass. "R" means radial. "B" in place of the "R" means the tire is belted bias construction. "D" in place of the "R" means diagonal bias construction. "16" Rim Diameter: The diameter of the wheel in inches. "92" Load Index: Load Index is a rating which reflects the load capacity of the tire. "V"Speed Rating: This tire has an industry-standard maximum service speed of 149 mph. Tires using an older European system carry the speed rating in the size description: 215/65HR15. Different letters correspond to different maximum service speeds. For a complete listing of Speed Ratings. The letters "DOT" certify compliance with all applicable safety standards established by the U.S. Department of Transportation (DOT). Adjacent to this is a tire identification or serial number; a combination of numbers and letters with up to 12 digits. The sidewall also shows the type of cord and number of plies in the sidewall and under the tread.			Light Truck Sidewall Information "LT" stands for Light Truck "LT235/85R16" is the size designation for a metric light truck tire "LOAD RANGE" identifies the load and inflation limits "RADIAL" indicates that the tire has a radial construction "MAX. LOAD SINGLE 2623 lbs. AT 65 psi COLD" indicates the maximum load rating of the tire and corresponding minimum cold inflation pressure when used in a dual configuration. The other markings on the sidewall have the same meaning as described for the passenger car tire. Uniform Tire Quality Grading System (UTQG) Except for snow tires, the DOT requires the manufacturers to grade passenger car tires based on three performance factors: tread wear, traction, and temperature resistance. Tread Wear More Than 300: Better 300: Baseline Less Than 300: 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 of their use and may vary due to driving habits, service practices, 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. For More Tire Safety Information visit National Highway Safety Administration Rubber Manufacturers Association