Tire pressure is a vehicle's recommended cold tire inflation pressure. It is measured in bars or PSI (pounds per square inch).
Example: 215/55 R16 91 T
215 is the tire width in mm
55 is the ratio of profile height to width or simply 'profile'. With the same width, the larger this indicator, the higher the tire will be and vice versa
16 - diameter of the wheel (disk) in inches. (It is the diameter, not the radius!). This is the inner size of the tire or the outer size of the rim
91 - load index. This is the level of maximum permissible load on one wheel
T - tire speed index