This text comes partly from Wikipedia

Tire-pressure gauge

A tire-pressure gauge is a pressure gauge used to measure the pressure of tires on a vehicle.

Environmental conditions can introduce a 13% to 15% variability in pressure due to temperature (0 °C to 40 °C), and additional changes can result due to altitude. Most car owner manuals do not state rated pressure as a function of temperature or altitude and leave it to the user to make appropriate measurements.

Since tires are rated for specific loads at certain pressure, it is important to keep the pressure of the tire at the optimal amount. Tires are rated for their optimal pressure when cold, meaning before the tire has been driven on for the day and allowed to heat up, which ultimately changes the internal pressure of the tire due to the expansion of gases. The accuracy of a typical mechanical gauge as shown is ±3 psi. Higher accuracy gauges with ±1 psi accuracy can also be obtained.

Measuring the tyre-pressure
Tyre-pressure has to be measured before starting with driving.The official mentioned pressure according to tyre- and car manufactureres, is based on an outside temperature of +20°C. With every 10°C there is a difference of 0,1 bar pressure. When we measure the pressure at zero degrees Celsius, the pressure will be 0,2 bar than with an outside temperature of  +20°C. To compensate the influence of low outside temperature, most tyremanufacturers advice to raise the pressure by 0,1 bar for every 10 degrees lower than with the usual pressure.

Look for our Pelican Tyrepressure Gauge after clicking on the button to Energy Saving