Tyre pressure gauges are used to measure the pressure of the tyres on a vehicle. Some tyres are rated to specific loads at certain pressures, it is important to keep the pressure of the tyre at the optimal rating.There are three types of pressure gauges: Stick: These are long metal sticks with rods that slide out of the valve end and connects to the valve stem of the tyre. To use it, take the open end of the stick gauge valve and press firmly. The white stem begins to push out the other end and indicate a number, probably between 20 PSI and 40 PSI. Dial: These gauges have a small clock like faces on them that resemble a speedometer. After taking off the valve cap on the tyre, apply the valve end of the gauge. Wait for the needle on the face to stop moving to read the pressure. Digital: These gauges are similar to dial gauges, but they use an electronic LCD display to show the pressure.