i just got 4 new Nitto Terragrapplers tires and they say on the side wall that they can be inflated up to 65 psi. i kno that the only reason they can be inflated to that high pressure is so that more weight can be put on them. the question i have is what pressure should i be running in them. right now i am running around 45 psi. is there some sort of equation or formula that can help me figure out how much to inflate them to, for maximum tire life?