This from a rv.net member found out from actual experience about low pressure = higher tire temps along with more rolling resistance when derating commercial grade G or H or J tires.
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Posted: 04/27/17 08:01am Link | Quote | Print | Notify Moderator
***When it came time for me to replace our tires, I researched many different ways to go. I wound up purchasing 17.5" J rated medium duty truck tires and wheels. When all done and said, it was $5.00 per wheel and tire combo more than just replaceing the 16" tires. This tire and wheel combo is good for 6005 pounds each. Using the inflation chart to get the pressure for the load, I inflated to 80 psi which was good for 4500 pounds per tire. With the first tow with these tires to Kansas City, I have made this trip to the speedway several times before, I was down almost 2 mpg both ways. The tires were 20*-25* hotter than the truck, which I have never experienced before. I inflated them to the side wall pressure, 125 psi for max load, before our trip to Florida. Now the tires run 5*-10* cooler than the truck and my fuel mileage is back where it used to be. I have always run max pressure up until I installed these tires, with what I have experienced, I will continue to run what the side wall indicates.***
Now add expert advice from actual tire engineers on the subject of interply shear forces and internal carcass/tread belt damage ......and minimum pressure charts Tireman9 and Capriracer has tried to educate us for years.
Over tiring a trailer 35% above 4500 lb wheel loads leads to speculations on the best air pressures for a 6008 lb rated 18 ply tire. I'll speculate maybe 110-115 psi at a minimum.
