Most, if not all, tractor tire manufacturers publish charts with the specs for load capacity at various inflation pressures because they know that the tires are used for load carrying and traction, with the more important of those two varying depending on the application. Lower pressure is better for traction as it puts more bars on the ground. Higher pressure is better for load carrying as it increases load carrying capacity. There is some expectation by tractor tire manufacturers that the end user will apply some thought and research to tire ballasting and inflation to fit the job at hand. They don’t normally print the entire spec sheet for the tire in the sidewall. Maybe they should, but it would be pretty hard to read on the smaller tires.
Example:
https://commercial.firestone.com/co...bles/Mar2015/Load and Inflation - Table E.pdf
High load (fronts on a tractor with loader) = max pressure as spec’d by tire manufacturer. More traction with max weight capacity not needed (possibly rears, depending on use) = possibly lower pressure than max rated.
For a basic discussion of tire pressure considerations for tractor tires (although it is also discusses tire type):
Radial tractor tires provide your farm with several advantages over older bias-ply tractor tires, including higher load capacities and longer wear.
www.ntstiresupply.com
Run your tires at whatever pressure you want so long as it doesn’t exceed max on the sidewall. But if you want optimal performance, think a little about what you’re doing with the machine and what tire pressure is appropriate based on tire type and use.
The above has nothing to do with car, truck, airplane, or other type tires. High speed tires are a different topic. If you want to argue with the above in regard to tractor tires, take it up with the engineers at Firestone or Titan.