Heavy-loads and high speeds, combined with underinflated tires can make for an on-road catastrophe. The excessive heat being generated by an underinflated tire due to the increased flexing of the tire sidewalls in combination with the longer footprint leads to rubber compounds failing.
Air pressure is based on the worst-case load the tire will see in the real world. The tire companies all publish load/inflation tables that identify the proper tire pressure for a given load depending if the tire is being run as a single or dual.
When it comes to proper pressure–steer tires have the best tire pressure of all wheel positions, according to industry surveys, which is good because low steer tires are a serious safety issue. Drive tires are next in the inflation pecking order, with outside duals typically have better pressures compared to the inside duals. Trailer tires always have the poorest inflation pressure for several reasons. Maintenance may not see a trailer for weeks, months or even a year.
Driver education regarding accuracy of tire pressure gauges should be mandatory training. So-called Tire thumpers may reveal a tire within 5 or 10 PSI, but it is nearly impossible to distinguish between a tire with 70, 80, 90, 100 or 110 PSI. The stick pressure gauge is the most common tire pressure gauge. The issue with stick gauges is their accuracy. Regardless of manufacturer, stick gauges are only accurate to plus-or-minus (+/-) 3 PSI brand new out of the box.
Using a brand new pressure gauge may reveal a tire with actual 100 PSI to be 97 PSI, and the same tire with a second gauge may give an answer of 103 PSI. Dropping a gauge a few times on the hard concrete surface can change the accuracy very quickly to +/- 5 PSI.
Pressure gauges need to be checked for accuracy using a master gauge or air gauge certified station. If it is not accurate, the best solution is to throw it away.