First of all what size are your tires and rims. Also what letter designation is on the tires such as E,D or C. I know most LT tires are E but I do not want to assume. On your tires should be a recommend weight/air pressure setting such as 3195LBS at 80PSI. IF so this is the recommend maximum air pressure setting of your tire.
Now the best thing to do is to weigh your truck and trailer on a certified scale. With this information you can determine the proper air pressure to support the load that the truck is carrying when towing. Your tire dealer and or tire manufacture can provides an air inflation table showing what the tires will support at what air pressure. Ask your tire dealer what is the minimum air pressure to use in your tires when you are empty. Anything lower than that pressure and you can ruin the tires.
2016 34RL CC; 2008 Ram Mega Cab 2500HD, 6.7L, 68RFE 6 speed, 4X4, Smarty S67, 100K+miles