Thanks!!

 

Max air psi depends on the max load rating of the tire & thas on the tire sidewall. 40-45 PSI is a good stab on a F150 is my thought. Maybe 42 all around gives warm weather operation with the PSI raising as you drive on the pavement. I would say watch the dash occasionally to see what they are doing and if you are approaching the max PSI/Load rating U can always drop a couple PSI.

 

Hate to say it, but that's not how tire ratings work.

Every spec you ever read for pressure is when the tire is cold, and those are calculated under the assumption that the tires will heat up during normal operation. You never want to adjust a tire as it warms up, it is perfectly acceptable for the tire to exceed the maximum pressure while in operation. That is calculated into the pressure rating.

 

As stated, the sidewall is the MAX pressure for the max load rating of each particular tire, not what it calls for under normal everyday use. The best and most accurate DIY way is to do a tire chalk test. Videos all over youtube. I went from P275/65-18 stock tires to LT275/70-18 tires on my 2008. The stock tire pressure was 35 psi cold. I did the chalk test on my LT replacement tires and they were best at 42-43 psi cold. The MAX pressure was 80 psi for max load rating. Sadly, there are still people confused on this who run 70-80 psi because "it's what the tire calls for". Might as well fill them with cement at that point.