When I check my hub and tires, I expect to find that the temperatures are similar between hubs and between tires. I also expect to find very little difference between hub and tire. For a reference, I check the Tow Vehicle wheels and tires.
A couple of things to think about:
- If you have a turbo, the wheel and tire on that side of your truck will be warmer than the others.
- If the sun is bright and predominantly hitting one side, you will see higher temps on that side.
- If the trailer is not level (more load on one axle than another) you will see a slight difference in temperature.
I have been using the IR therm. for several years. It provides interesting information.