The recommended tire pressure of the vehicle is determined jointly by the vehicle manufacturer and the tire manufacturer. The recommended tire pressure for your vehicle tire combination can be found in your vehicle manual, on the inside of the fuel tank cap or on the doorpost of the driver's seat.
Tire pressure affects many important aspects of vehicle performance, such as driving comfort, directional stability, steering and brake grip, and overall handling performance.
Driving a vehicle with poor tire pressure can adversely affect these important characteristics.
Generally, tires lose one pound per square inch of pressure per month, so it is best to check the tire pressure before long trips, and even the spare tires should be inspected.