I'm assuming empty but a co-worker says the pressure in the tires will be higher after it is loaded (if you pump tires to max psi, they will be over max psi and then when they heat up they will be way over). He is probably right but is it a negligible difference, anyone know?
Your co-workers owners manual for his/her truck provides inflation values for the load carried. The lighter the load the less air inflation value, the more the load the higher the inflation value. I would think that if your co-worker was correct the lower values unloaded would increase naturally with the load to the higher values, but it does not. Adding more air for more load is counter to his/her reasoning.
When I carried a 4000 pound cabover camper on my truck I ran 80 psi cold in the tires. Lightly loaded with no camper or loaded with the camper 80 psi was 80 psi -- the value was the same.
The cold air pressure check is the tire manufacturer's recommendation and that value takes into consideration that heat will increase the pressure a little once on the road. Never release pressure to compensate for heat or the tire will be essentially operating underinflated.
Altitude slightly changes tire pressures but it is insignificant for most RVers making it is a non issue.
If you want to run nitrogen in tires there are some benefits -- less water content than air, less heat increase re pressure and altitude makes a lesser difference.
