BEFORE USING YOUR DEFLATORS 1.Firstly it is important to understand that not all tyre pressure gauges are equal . Gauges can vary from each other by up to 10% or more , and they can also be inaccurate . Select a quality gauge with a narrow pressure range for greater accuracy and you will find that the differences between your Tire Deflator settings and the actual pressure reading ( from your gauge ) will be minimal . You should expect up to 2psi as being an acceptable variation . 2.By using the same gauge , and setting the Tire Deflator graduated barrel in a consistent manner , you will obtain reliable results each and every time . 3. The 10PSI- 30PSI adjustable range allows you to set the Tire Deflator to suit most off-road driving conditions . 4.Some units will start deflating immediately when they are attached to the tire valve , especially at lower pressure settings ;Others need the plunger to be lifted to commence deflation . Both situations are normal ;The valve will stop at the set pressure regardless . 5. The Tire Deflators can deflate four tire at once to a desired setting from 10psi to 30psi in half the time compared to conventional valve removal tire deflators.