So I was talking to my FIL today about tractors and tire pressure came up, he said the old farmer method for air pressure in loaded tires goes by the tire size. In other words, my new tractor has 12-16.5 rears, so he said I will want to be right around 16 to 17 pounds in them. Our White 2-85 has 22.5 tires and we run 22 lbs in them. Just a quick way to tell if you are running proper air pressure according to a wise old farmer. Makes sense to me because a farm tire guy loaded my tires and they have 17 lbs of air in them.