Cold tire absolute pressure (gauge pressure plus atmospheric pressure) varies directly with the absolute temperature, measured in kelvin.įrom physics, the ideal gas law states that PV = nRT, where P is absolute pressure, T is absolute temperature, V is the volume (assumed to be relatively constant in the case of a tire), and nR is constant for a given number of molecules of gas. Tire pressure is commonly measured in psi in the imperial and US customary systems, bar, which is deprecated but accepted for use with SI or the kilopascal (kPa), which is an SI unit.Īmbient temperature affects the cold tire pressure. Excessive pressure, on the other hand, will lead to impact-breaks, decreased braking performance, and cause increased wear on the center part of the tread surface.
DO TIRE PSI RISE AND FALL WITH AIR PRESSURE DRIVERS
Drivers are encouraged to make sure their tires are adequately inflated, as under inflated tires can greatly reduce fuel economy, increase emissions, cause increased wear on the edges of the tread surface, and can lead to overheating and premature failure of the tire. 40% of passenger cars have at least one tire under-inflated by 6 psi or more. Most passenger cars are recommended to have a tire pressure of 30 to 35 pounds per square inch when not warmed by driving. Recommended cold inflation pressure is displayed on the owner's manual and on the placard (or sticker) attached to the vehicle door edge, pillar, glovebox door or fuel filler flap. A tyre pressure gauge displaying bar (outside) and Pounds per square inch (inside)Ĭold inflation pressure is the inflation pressure of tires before a car is driven and the tires (tyres) warmed up.
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