[77newell]

Our tire pressures are best when the tire pressure is set to match the carried load. The only reason to raise them above the pressure needed to carry the load is to have a margin for load and temperature variations. If your load varies little and you regularly check your tire pressures each morning, the manufacturer would say you gain nothing by increasing the pressure. And your ride will be stiffer.

Another point is that as tire grades (G and H, etc) rise the weight carrying capacity of the tires is identical (for the same size tire, eg: 11R24.5) for any given pressure. In other words, at 105 psi both the load range G and H tires will support the same weight according to the manufacturer. In fact, most manufacturer's tires carry the same weight at 105psi.

In order to run at a lower pressure for a given carried weight you would have to change tire sizes, usually to a wider tire. As the tire pressure is spread over a larger contact area the psi can be lower. In fact this is what happens when our tires are underinflated, the contact area increases, but the sidewall ends up flexing a whole lot more and that produces the heat the eventually destroys the tire. The load/psi charts are designed to carry the load (probably keeping the contact patch constant) while keeping the sidewall flexing limited to an allowable level.