I bought new tires for my truck and now I'm wondering what is the proper tire inflation. Please, don't just tell me to look at the owner's manual or door sticker. I want to know how to calculate the proper tire pressure based on the tire and the weight of the vehicle.
For example, what should the pressure be when I'm running empty and the vehicle is at its lightest and what should it be when its fully loaded with cargo.
Now for specifics on my truck. Its a 2000 Chevy Silverado Z71 4x4. The owners manual and door sticker say original tires are P265/75 R16 Load Range C. However the truck came from dealer with LT265/75R16 LRD and Load Rating somewhere around 118. I ran these tires for 60k miles using 45lbs psi.
My new tires are LT265/75 R16 LRE, Load rating of 123. (The tires I wanted didn't come in LRD and I didn't want to go down a rating.) I asked the tire dealer what inflation they recommended. Of course they said 35lbs after reading the door sticker. I had them put 45lbs as I shook my head
So, back to my question. For a given weight on a given tire what is the proper tire pressure to get the proper contact surface with the road?