Different issue, and does not apply here, but I have noticed that at least after parking for a while, the pressure difference between the pair of wheels with direct sun versus the pair of wheels in the shade can easily be 3-4 psi because of heating by sun.
I could see all kinds of things causing the extra heat on the inside wheels, much of which falls into the category of air circulation as mentioned by Lt. Dan. The brake drum/rotor is inside the inner wheels, the outer wheels do not get exposed to brake heat. The inner wheel has a drum/rotor on one side and a tire on the other to block good airflow. The outer tire has a tire on one side, but open to air on the other to allow cooling.
The crown of road is a good one, I would not have considered probably.
Where does your exhaust pipe run in relation to wheels? I would expect one side of coach only, so that side maybe a tad warmer, but I think this and engine heat are the least of the issues.
2020 Chevy Silverado 1500
Forest River Wildwood XLite 263BHXL