What tire pressure to run?

Since this is an E350 van, it certainly was designed for LT-E rated tires from the factory, so the door sticker numbers are appropriate.

Door sticker says 55PSI front, 80PSI rear for LT-E rated tires.

So asking/arguing about it is a complete waste of time and breath, at least on the rear: 80PSI is max sidewall pressure, and the recommended pressure on the door sticker. Somehow you guys will still figure out a way to argue about which is right and which is wrong, though.

The PSI ratings are based on the maximum load the truck/van is designed to carry on each axle. These are in turn based off the tire manufacturer's inflation tables, which are pretty much the same from manufacturer to manufacturer when you are comparing apples to apples: That is, a 245/75R16 LT-E to another manufacturer's 245/75R16 LT-E, for example.

Kind of a how heavy is my rock question with no specifics.

Load E tires may be a LT225/75-16 at 2680 lbs capacity or a LT305/75-16 tire at 3500-3700 lbs capacity. How much weight the truck/van is carrying when loaded vs when not carrying a load means different pressures. And yes it can means a lot of difference.
Some folks just pump them to the max and replace them in 30k-40k miles.

I air my tires on my trucks to the pressure for the load. I usually run load E truck tires for 70k-80k miles and always change tires just before the wear bars show.
However I know all my vehicles loaded and unloaded axle weights and I have my own compressor so airing up or down is no problem.

Without any specifics on your tire sizes and axle loads just pump them to the max and hope for the best long term service.

I run mine at 60 psi, that's enough to carry 2800 lbs per tire.

OK, let's get out the slide rule and a couple of calculators...and adjust for sea level and ambient temperature...just kidding, run at max pressure and you will not run the very real risk of running on underinflated tires.

It depends. You can:

1. Inflate your tires to your manufacturer's recommended pressure as listed on the sticker on your door. This is the recommended pressure for maximum load, though, so it might not give the best ride or traction. But it should be perfectly acceptable to run them at the door sticker pressure while towing instead of at max sidewall.

2. Weigh your rig's axles separately. Divide each axle weight by 2. That's how much each tire should carry. Alternatively, find a place that lets you weigh all 4 tires separately. Go to the tire manufacturer's website and find the load inflation tables. Use that to find the appropriate inflation value for said weight. Inflate your tires to that pressure. This will give you the best ride and the recommended contact patch between the road and your tires. Be aware that you'll have to up the pressure if you add any cargo.

The LeRoys wrote:
I've always run my tire pressure at the max that is on the sidewalls of the tire, especially when towing. My tires are Michelin LTX MS2 tires, and have a max of 80psi. Should I be running them at the max? Or run them at the sticker on the side of the vehicle door? What difference will it make?

To give you the correct answer we need a bit more information.

What is the weight rating at 80psi, from the side wall?
What do you axles weigh towing and not towing?

Running "E" rated tires at max pressure without max load, is over inflating, this reduces traction for starting, wet conditions and braking.

My example the rears on my 2001 Ram 2500 are 265/75-16E's 3,415# capacity or 6,830# for the axle. My rear axle weighs in at 5,500# loaded, I run between 65 and 70 psi, no issues and great traction.
Empty I drop to between 45 and 50 psi.

If the door sticker says 35 psi; you'd likely damage the sidewalls of those 80 psi tires. Just run them at 80 and have peace of mind knowing the pressure is not too low and they are not under inflated.

I always run mine as stated on the side wall of the tire.