Wogster

It depends on a number of factors, generally though the articles are right, but the pressure tables don't go high enough. Fill the tires to the maximum pressure, measure from the edge of the rim to the ground, multiply this by .85, get on the bicycle and measure again, if the number is more then you calculated, you can drop a little pressure until it matches up, if it's below that amount, then you need a higher PSI or a wider tire at the same PSI. The width of the tire and the height of the tire are almost the same, most pressure gauges are ± 5 PSI, you never will get it exact, but it will be close enough. You just want to make sure you stay above the minimum.

Unfortunately the bicycle tire industry tends to make the assumption that all riders are under 140lbs, so you see things like a tire in wider widths having lower pressure ratings so that you can't use a wider tire to handle more weight. I also find it interesting that a frame will be designed to hold up a 500lbs rider then have chainstays that only allow a 23mm wide tire, a tire that would need to contain over 170PSI to hold the load.