Correct Dually Air Pressure

I think it is a personal preference and balancing act. At one point I tried running the higher psi in the rear tires and noticed I was getting crown wear. 65 - 70 is just fine on my rig.

What is the load capacity of the tires at 65#??

At 80# each that's 11,332# total.....that's 2532# more than needed and tires would be over-inflated causing the center of thread to wear.

Look up tire load chart for your brand/size tires

65# will probably give you full rear axle load capacity.

Go with the door jam #65. #80 would most likely be a little to high and as said cause crowning problems with tires.

If you run lower pressure while heavy you run into a chance of sidewalls touching under some conditions. My Dodge tire spacing is less than I would like when heavy but never had a problem. Pick up rocks and fling them also. Just saying.

Always go with what the tire says is max PSI. Door sticker is for comfort not load carrying. Especially true if you have changed tires since the truck was new.
I Up my PSI by 20LBS when I am towing or hauling my TC.

Running the max pressure just because is silly. Look up the proper inflation for your tires with a load inflation chart provided by the manufacturer. Since your load is well under your rated axle weight I suspect that 65 psi is more than enough. Increasing the pressure will only wear out the center of the tire faster and provide a harsher ride.
My truck with camper on it weights in at 13,140 pounds with about 8,800 on the rear axle, that's 300 pounds over the RAWR but the tires will support that weight at 70 psi according to the chart so that's what I run. When I hitch up the boat it adds about 400 pounds on the rear axle. I increase the pressure to 75 psi when towing the boat. The truck rides really nice and the tires are wearing extremely well. I've gotten over 50,000 miles out of these tires and they still have a lot of tread left.

I hauled truck campers on my dually Dodge for 8 years. I always ran the max air pressure to help with stability in the sidewalls.

Yes, that does make the centers wear quicker but that's a price I'm willing to pay for the better handling and decreased risk of sidewall failure.

I still got 65K miles on the OEM installed Goodyear tires.

racerguy, but what was your dentist bill for all the replaced fillings? LOL!

The numbers shown on the door jam are sufficient to get the load rating for the vehicle. The number on the tire is the maximum pressure you can safely use in it. SWR use is usually at the max listed on the tire. On a dually, the only thing you'll gain by going to 80 psi is a slightly stiffer ride (probably won't notice this unless your springs are really compressed) and crowning in the center of the tire. This actually reduces the control because not as much rubber is in contact with the road- stability won't change, and you're likely to be hurting the vehicle performance by overinflating.

On any vehicle, to obtain maximum traction and control, you have to match the load to the tire's contact. The best way to do this is to load the vehicle, then take some chalk and make a mark about an inch wide across the tread. Drive straight for 10 or 20 yards (may have to adjest the distance depending on the roughness of the surface), then take a look at the remaining chalk. If its worn away uniformly, the tire is at the correct pressure. If there's more left in the center, the tire is underinflated (edges are carrying more of the load). More chalk left on the edges shows crowning, soi you need to reduce the pressure. Adjust the pressure until you get uniform wear. Do this for both front and rear tires. Unless the load changes significantly from one trip to another, you only have to do this once, then use that pressure next time. With my setup, there's about a 10 psi difference in the rear loaded versus unloaded; front is pretty much the same.