It can be a bit confusing, but I'll try and explain. Tire manufacturers publish tire load and inflation tables for tires they manufacture. In a perfect world you would know what the actual load is being placed on the tires and could go to the load and inflation tables for precise inflation pressure.
Since we know this isn't always practical there are a couple of ways to help determine tire inflation pressure. On the front left corner of the travel trailer you will find a Federal Certification Tag or label. This label displays information on tire inflation pressure, GVWR and GAWR. The tire inflation you see on the label is based on what the trailer weighed when it was built. If no additional weight is placed on tires this inflation pressure is accurate, but we all add weight to the RV when we load it for a trip. The question is how much weight is added and the only answer to that is to have the RV weighed, preferably by individual wheel position.
The inflation pressure molded into the sidewall of the tire is the maximum amount of air pressure you would ever inflate the tire to if a full load was placed on the tire. You can find the tires max load range on the sidewall too.
What this means is, if the trailer tires are not overloaded the inflation pressure (depending on actual weights) is somewhere between what is posted on the certification label and molded in the tire sidewall. In other words in some cases it is possible to increase tire load capacity by increasing the inflation pressure in your tires, but you cannot exceed the maximum pressure specified on the sidewall of the tire. You can usually find load and inflation tables on the internet.
It’s also important that you use the same inflation pressure on both ends of each axle. If you weigh the RV and the tire loads are different on each axle end the load tables might require different inflation pressures. When this happens you need to redistribute the load. If the load can not be redistributed you would inflate both of the tires to that axle to the inflation pressure required for the tire with the heaviest load. Keep in mind that it cannot exceed the max tire pressure molded in the sidewall.
Here are a few general rules for tire inflation I like to use:
- Never pull the trailer with tires inflated to less pressure than required for the load placed on the tires.
- Never pull the trailer with tires inflated to less pressure than what is on the certification tag, no matter what the load.
- Never inflate your tires above the maximum pressure shown on the tire sidewalls.
Happy RV Learning,