2009年1月19日 · Correct pressure is 20-100 psi. The "rule of thumb", he said, is to use 1 psi for each 50 lbs. of weight on each rear wheel set. His example was that if the total loaded weight on the rear axle was 8000 lbs., then divide by 2 for the weight per side, then divide by 50, resulting in a correct pressure of 80 psi in each air bag.