Tire pressure's listed on door jamb pertain to tires that came on vehicle originally. It would be ridiculous to believe that's an across the board, broad strokes answer that pertains to ALL tires, even those of different size/ply ratings/ect. Chalk testing is only a tool used to get MORE information on proper PSI. Wear characteristics, gas mileage, ride comfort, and overall handling have to be considered as well. The age old "I bought XXXX so XXXX must be the best" argument doesn't hold water in my estimation. I've had Duratracs. They CAN perform well, but I had to jump through too many hoops to make 'em work. Frequent re-balancing, Rotation every 3000 miles, ect...I got almost 70K wear, but they rode rough from day one. (265/75r16 load range C) I've had KO2's and KM2's. (KO's load range D, KM's load range E) My opinion was, avoid wet roads. Avoid loads on the KM's. (Squirmy even at high pressures) I have had extremely GOOD luck and performance from 2 sets of Cooper STT PRO's (285/75r16, load range E) Chalk test says 31 psi. Other indicators say 35 to 37. I run 35 F & R. Cooper says these are 40K tires. 1st set went over 60K and was still a very good tire. Long story short, I wasn't overly impressed with either Duratrac's OR KO/KM BFG's. Between the two, would go Duratrac....But there are better choices.