You do not need to weigh your RV every trip. You also do not need to adjust tire inflation each trip.
Unless you are making significant (1,000# or more) changes in what you pack in your RV, I see no reason to be messing with tire inflation once you have been on a scale to learn the actual load on your tires.
The general advice for weighing is to have the RV loaded to the heaviest weight you expect to travel with. This means full of clothes, books, tools, water, fuel, food, spare parts, bowling balls, and toys you might travel with.
One important inflation number
There is really only one inflation number you need to keep in mind and that is the MINIMUM inflation required to support your load. We are trying to protect the tire from failure and historical data from RVSEF shows that over half of RVs have been running one or more tires in overload.
Damage to the tire structure is caused by the rubber bending and stretching past an elastic limit at the molecular level. This stretching actually breaks some of the chemical bonds. Once broken, the resultant cracks never repair or reform themselves. They will start small cracks between the belt edges, as seen here in picture #1
The cracks can only grow. Once formed, the cracks will just get larger and larger until, eventually, they get large enough to result in a failure of the structure. Many times that is in the form of a belt detachment from the body of the tire, as seen here in picture #2.
Or, even worse, they can result in a complete tread separation aka “blowout,” as illustrated in picture #3, that is from a different RV trailer.
It doesn’t take too many miles for a tire in this condition to come apart. You may end up with a nice “blowout” unless the tire is replaced before the crack gets too big. The tire in pictures #1 and #2 above did not come apart, but there were bulges observed during a “free-spin inspection.” You can learn more about inspecting tires HERE. There is even a YouTube video showing the “wobble” in tire #1.
Load & Inflation charts
The inflation in the Load & Inflation chart is the MINIMUM you should run. But heat, age, and the tearing a tire experiences from hitting potholes can result in the rubber cracks forming even if you are running the inflation found in the charts. Running higher than the minimum inflation can offer some protection as the tire will run cooler and bend less, which means less tearing of the rubber chemical bonds.
If you look at the tables, you can see that each increase of 5 psi gives you a few hundred pounds more load capacity. Conversely, each drop of 5 psi decreases the load capacity of your tires.
Tandem axle trailers place some additional stress, called interply shear, on the tires. That results in more cracking and more tearing of the rubber bonds.
Don’t adjust tire inflation below this
I would recommend against lowering tire inflation once you have learned the inflation required to support your heaviest weight. I also recommend that you set your TPMS low-pressure warning level to no lower than 5 psi below the minimum inflation learned from your scale reading. There is no reason or benefit I can think of to ever adjust tire inflation to lower than what is needed to support the load. In fact, on my RV, I run my inflation at a +10% margin over the inflation from the tables. This allows me to set the TPMS low-pressure warning level to the inflation required to support my heaviest scale reading.
Have a tire question? Ask Roger on his new RV Tires Forum here. It’s hosted by RVtravel.com and moderated by Roger. He’ll be happy to help you.