I'm guessing the letters mean Load Range E Mud + Snow.
Managing tire pressure in truck tires is different than car tires. In a car the load doesn't vary to the degree that it can in a truck so the pressure is always maintained to a set recommendation. A truck tire's pressure is determined by the load the tire carries. Too little pressure for a given load causes the side walls to bulge out and flex as the tire rolls. This flexing generates heat - enough heat to cause a blow out
Losing a tread on a truck tire is not only dangerous it can cause major damage to your RV. And, too much pressure can result in a harsh ride, excess tire wear on the crowns and a reduction of traction. Please visit Bill Hemme's post in the technical library, download the pdf chart and print it out to keep handy in your BF. http://www.bornfreervclub.org/bulletin_ ... .php?t=394
I believe you have a Flying Js in Bakersfield. They usually have a scale you can use to measure the weight of each axle on your BF for a small fee. Do this after your BF is loaded and before you leave on your trip. Its best to know the weight of each corner but not always easy to find a scale that will allow you to do this. Don't stop at a truck scale along the interstate - they'll chew you out for wasting their time.
The 80 you see on the tire is the minimum pressure at the maximum load carrying capacity of the tire. There are minor exceptions but generally this is the pressure you should not exceed. I'm not sure what the door panel sticker is telling you - probably the pressure at GAWR (Gross Axle Weight Rating).
After weighing the rig for different trips you'll begin to get a sense of what it weighs when loaded.
With the diesel engine and a generator our RSB is maxed out on the front axle and close to max on the rear. I fill the tires to about 5-10 lbs more than the chart's minimum recommendation (70 rear/75 front). We're usually in the mtns where temperatures can vary dramatically.
On the road check the pressure often. When the tires are warm do not adjust the pressure to the cold pressure but look for large differences in heat and low pressure from tire to tire.
Mike