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Archive for March 2nd, 2009
G395, G316 and G305 proper air psi for long haul at max (80,000) weight.
Posted by JR from Western Grove, AR, US on March 2, 2009
I have read through several of your answers to others questions and followed your recommendation of checking your load chart. But I am not sure of my results: 34,000 (max weight) divided by 8 tires = 4250 lbs. per tire. Following your second 295/75/22.5 column (not sure the difference as they both are listed the same) 4,300 lbs would indicate a tire psi of 75. That seems too low, am I correct or should I run this pressure for best fuel economy and tire wear? (These tires were rated at 75mph, so if I understood correctly, no adjustment is needed for speed). I came up with 105psi for the fronts at close to 12,000 lbs / 2 tires, which is more in line with what I expected. Thanks in advance for your help!
You have done all the math correctly and you are correct about the recommended inflation pressure for the loads being carried. In order to make life simple for the people taking care of tires, many fleets specify one inflation pressure for all tires and use the pressure required by the tires carrying the largest load. This is almost always the steer tires. So, you are correct, the pressure shown on the load/inflation table seems very low but, in fact, is the correct pressure required for the load being carried. We always urge fleet to error on the high side so, setting pressures 5 - 10 psi higher than what is required is a good idea and will improve fuel economy. Tire wear is optimized when the recommended pressure is consistantly maintained.