• Uniform Tire Quality Grading System• Fundamental characteristics of tires• Tire safety tips.Use this information to make tire safety a regular part of your vehicle maintenanceroutine. Recognize that the time you spend is minimal compared with theinconvenience and safety consequences of a flat tire or other tire failure.6.4.1 Safety first–Basic tire maintenanceProperly maintained tires improve the steering, stopping, traction, and load-carrying capability of your vehicle. Under-inflated tires and overloaded vehiclesare a major cause of tire failure. Therefore, as mentioned above, to avoid flat tiresand other types of tire failure, you should maintain proper tire pressure, observetire and vehicle load limits, avoid road hazards, and regularly inspect your tires.6.4.2 Finding your vehicle’s recommended tire pressure and load limitsTire information placards and vehicle certification labels contain information ontires and load limits. These labels indicate the vehicle manufacturer’s informationincluding:• Recommended tire size• Recommended tire inflation pressure• Vehicle capacity weight (VCW–the maximum occupant and cargo weight avehicle is designed to carry)• Front and rear gross axle weight ratings (GAWR– the maximum weight theaxle systems are designed to carry).Both placards and certification labels are permanently attached to the trailer nearthe left front.6.4.3 Understanding tire pressure and load limitsTire inflation pressure is the level of air in the tire that provides it with load-carrying capacity and affects the overall performance of the vehicle. The tireinflation pressure is a number that indicates the amount of air pressure– measuredin pounds per square inch (psi)–a tire requires to be properly inflated. (You willalso find this number on the vehicle information placard expressed in kilopascals(kPa), which is the metric measure used internationally.)Manufacturers of passenger vehicles and light trucks determine this numberbased on the vehicle’s design load limit, that is, the greatest amount of weight avehicle can safely carry and the vehicle’s tire size. The proper tire pressure foryour vehicle is referred to as the “recommended cold inflation pressure.” (As youwill read below, it is difficult to obtain the recommended tire pressure if your tiresare not cold.)Because tires are designed to be used on more than one type of vehicle, tiremanufacturers list the “maximum permissible inflation pressure” on the tiresidewall. This number is the greatest amount of air pressure that should ever beput in the tire under normal driving conditions.