OK, this is for street driving.
1. Take a piece of chalk
2. Draw a line across the tread on one tire
3. Move truck forward until the chalk begins to wear
-If it wears away on the outsides and stays in the middle, add air to the tire
-If it wears in the middle, but not the outsides, remove some air
4. Repeat steps 1-3 until the line all disappears at the same time
5. Write down that PSI
6. Repeat steps 1-5 for the remaining 3 tires
Do this while tires are warm (driven) to get it exact for normal driving.
I do this with my truck everytime I change the weight in my truck with 100 lbs or more. My front tires stay around 28 PSI and right rear is 32, and left rear is 35. This setup keeps the line disappearing equally across the tread on my tires. Yours will probably be different. This setup, IMO, keeps the tires from wearing irregularly. It takes all of 10 minutes after the first couple times. I keep the number written in my owners manual. Good luck!
