2 questions:

First, and most importantly, what tires are you running? Load range D or E? MT/AT? Size?

Second, do you have on-board air to re-inflate? If not, I think you'd do more damage to the tires running them under inflated to and from the trail at higher speeds than you would on the trail itself.

I'd say run them at full pressure unless you really need the extra traction off road or have on-board air to re-inflate them. Just be mindful of stumps. A good load range E or 10-ply mud terrain will have plenty of sidewall puncture resistance, even at full pressure.

 

I run a 285/70r17 Hurcules Dura-trac A/T Load range E 10 ply. i keep them at 44psi and drop them down to maybe 30psi when i go into the property. speed rarely exceeds 5mph...

As far as an onboard air compressor. i have a harbor freight one i keep in the truck thats really only good at inflating balloons at parties. my big compressor stays at home. i see a vai-air system in my future though...

ID

 

Given that, you're probably not gaining much going to 30psi. I'd just keep them at 44 so they don't get to hot on the drive there and back. They are plenty puncture resistant as-is and 44psi is a bit on the low side anyways.

 

I used the tire pressure calculation. Taking into consideration the weight of the truck and the load rating of each tire..the math says 40psi. I use 44 because that seems to low for an LT. when i was running 60psi i was getting 2 MPG better but i could tell the tires were riding on the centers. i can never seem to get a definite answer on tire psi. being as this is my first set of new tires ever (i always seem to find a good deal on a matching set of used tires with good tread) im overly paranoid on keeping these tires worn even and lasting me as long as possible...

 

In a way your talking about two different things.

You air down off road to increase contact patch and sidewall flexability over obstacles.

You air up with weight to prevent that sidewall and tread deflection at speed from generating too much heat damaging the tire. While not mutually exclusive, you really are trying to accomplish two different things. Hence carrying the weight off road and airing down is fine seeing as speeds are slow and you still want the increased traction while not generating the heat. As mentioned above though, as soon as you get back on road you need to get to proper pressure so you dont damage the tire, loose braking performance, etc.

A small compressor like a viair is fine. I prefer my PowerTank because I can generate greater pressure and run air-tools if need be. Sure, I do have to refill it periodically, but its only about $10 and takes all of 5-10 min at the place I use.

 

A small compressor like a viair is fine.

Hah if you've got the patience of a saint!! I'm with you on the PowerTank. I can't imagine filling up 34s to road psi with a portable compressor. I've got a big boy compressor in the garage for that.

 

I found this document from Toyo that has some really useful stuff on calculating loaded tire pressure by hand:

http://www.toyotires.ca/sites/default/files/loadinflationtable.pdf