I have a set of Staun tire deflators for sale that I no longer need since I sold my Jeep TJ. They are very handy for the trail head. All you have to do is set the desired pressure you like to run offroad (between 30 and 6 psi) and the deflators will stop letting air out when they reach that point.
Here is a link to stauns page with all the info and even a video of them in action:
4x4 tires
Let me know if interested at
thegper@msn.com or call eight one two-five three two-zero six two nine...or you can just PM me, Bryan