A baseline tire pressure is the recommended tire pressure, cold. In other words, it’s the tire pressure before your tires start rolling down the road.
There are two places which will give you an idea of what your tire pressures should be. The first is the permanently mounted placard containing max tire pressures, max load information, etc. This placard is similar to the one located on the driver’s side door jamb of most cars and trucks. The location of this placard will vary. The second is the max tire pressure located on the sidewall of your tire. It is very important that the cold tire pressure of your tire does not exceed the max tire pressure located on the side wall.
Another important factor in tire safety is weight. Tire pressures are greatly affected by weight! With the different load ratings, such as E, G, etc, tire pressure may increase at a faster rate, depending on the load rating of your tire. If you notice that your tire pressures are rapidly increasing, it is recommended that you weigh your RV and take into consideration the max load of your tires. It is also crucial to understand that even if your RV is under the max weight, it may not be loaded evenly. For example, if a double-axle travel trailer tire has a max load rating of 3,500 lbs., and the total weight of the travel trailer, loaded, is 12,00 lbs., it is still possible that one tire may be overloaded, depending on the disbursement of weight.
A great resource for tire inflation and load is the manufacturer of your tire. Each tire manufacturer provides load and inflation charts for ST (Special Trailer), LT (Light Truck), HD (Heavy Duty) or RV tires, located on their website.
The best way to know exactly what pressures to run is by having your vehicle professionally weighed. There are many excellent resources providing this service such as the RVSEF (www.RVSafety.com), as well as Escapees RV Club (www.escapees.com).