Sorry for the bump...just my two cents.
Basically, there is a set screw and a valve inside each deflator. You either tighten or loosen the set screw to the desired psi. They come pre set (~18psi), and each turn of the screw relates to a certain amount of psi. 3psi for each turn (approx)
The best idea is to use one tire and set your set of deflators. To do this
- you screw the deflator onto the valve stem
- depending upon where the deflator is presently set the deflator will either begin to deflate or you might have to pull the plunger out to start deflating
- check regularly the psi until you get to the psi you want
- screw down the set screw to stop deflation
- tighten locking screw and your done
- reinflate tire and repeat process with each deflator until you have done all four.
Now you will have one set that is set at a particular psi
Having another set, you can repeat the process for a different psi setting.
Now within that, you can also purchase Stauns https://mechanicguides.com/best-tire-deflators/
in three different psi ranges...
Light duty 0-10psi
Stndard duty 6-30psi (this is the one most 4x4 people use) - I'd like to two sets of these
Heavy Duty 15-55psi