Airing up or down on the trail is one of the basics to 4 wheeling, you almost always need to air down and when you get off the trail you need to get your air pressure back up so your tires don’t suffer the same fate so many Ford Explorer tires suffered. You can go with one of two options, first is onboard air, an air compressor and storage tank that you can fire up whenever you need the pressure, it’s a cool idea but pretty expensive since a decent compressor is in the $400-$500 range. Add another $80 for a tank, and $50 for plumbing and you have an expensive setup, not to mention that it can be damaged since it’s on the underside of the vehicle.
The second option is CO2. Carbon Dioxide stored as a compressed liquid can be used to fill tires, set beads on rims, and run power tools. Plus it’s removable when you don’t need it. All you need is a good place to keep it and a CO2 tank can serve all you air pressure needs.