Why does my tire pressure say psi?
Why does my tire pressure say psi? The acronym P.S.I. stands for Pounds per Square Inch. Generally speaking, it is the unit of measure inside a chamber containing gas. In the case of car tires, its the amount of pressure air exerts when inside of the tire. Why does my TPMS light say low tire pressure? So check your tires carefully. If your vehicle has a TPMS, it’s probably monitoring the pressure in your spare tire. Therefore, if you get a low tire pressure warning light, and if you’ve checked all four tires that are touching the ground, than you...