The best optiojn on that is to look at the tires and wheels you have on the truck. Each will tell you what the max pressure is for them. Example, if the tires say the max is 110 but the wheel is stamped for 80, do not exceed 80.
For the minimum pessure go to the tire manufacturers website or a store and look for the inflation chart for the make and model tire you have on the vehicle. This chart will give you the inflation per the load on the tires. To get the load go to a truck stop and weigh the truck, preferably one axle at a time. You need the axle weight as that will tell you what each one is carrying. The front axle will carry more weight than the rear when the truck is unloaded. Simply inlate to the charts limits per the weight on the tires. This will keep you in the inflation the tire was manufactured to deal with per the load.
Don't forget to increase the pressure before you load up or hitch up. In fact it's a good idea to weigh the trailer and truck so you make sure you stay within the guidelines of the truck and tire capacity when towing.
Mike Nancy and the fuzzies
Fulltiming since June 2004
Volvo 660 MH tow vehicle
2005 MS 38RL
2007 Saturn Ion "toad"
2010 Gold Wing "piggyback"