Tire pressure depends on Your Weight, Tire Brand & Sidewall construction. I run 10 psi in the dirt and 14 psi on blacktop. BUT I always check how much the tire is flexing when I put my weight / step on the tire/rim at the ground surface while the bike is at rest on the kickstand and when I sit on the bike under the load of my weight. I am on the lighter side and 4 lbs makes a world of diff in the bikes performance. Experiment with pressures and find what works for you. Start at 14 and drop a pound or two each time you go out. I too use heavy duty tubes.

rocmoc n AZ/Mexico