Correct tire pressure will lengthen the life of your tires and save you lots of money in the long run, make driving smoother and easier, and more safe. But, what is correct?
The correct tire pressure for each individual motorhome must be calculated. It cannot be “given to you” nor is it some standard setting related to tire size. Determining your RV tire pressure is very different than finding tire pressures on any other vehicle. Don’t assume or guess that you know the correct tire pressure for your motorhome. I know you regularly check your car’s tire pressures and probably use some tire pressure chart (often posted in the driver’s door), but the motorhome is different.
What’s My Correct Tire Pressure?
Two factors are used to calculate correct motorhome tire pressure—the tire size and the coach weight at each wheel position. “Whoa,” you say, “my tire pressure is stamped into the side of the tire.” True, but you can’t rely on that for two reasons. First, that is the minimum cold tire pressure allowed for the maximum load. Second, your RV tire pressure will be different for the front and rear (single and dual-tire pressures) even though your tires are the same size and stamped with the same pressure setting!
Think of it this way. When something is inflated (balloon, beach ball, or tire), the air pressure in that object can be measured. You measure this when you check your car’s tire pressure. When that same object is under external force (squeezing the balloon, sitting on the beach ball, or loading your RV), the amount of air pressure is increased since the object is being squeezed. The amount of air is the same—you did not add more air—but the space containing the air shrinks—becomes smaller—because it is being squeezed.
So, the major lesson here is that as you load your coach, your tire pressure increases. How much? Nobody knows. Therefore, your correct tire pressure cannot be calculated until the coach is fully loaded and each wheel position is weighed. What does “loaded” mean… fresh water, fuel, canned goods, food in the freezer, people, clothes, books, tools, dishes, your horseshoe collection, etc., and all the rest of your stuff!
Tire manufacturers provide charts to help you determine (calculate) correct single- and dual-tire pressures after weighing the individual wheel positions. Without knowing the wheel-position weights on your coach, you can only guess. Using those weights, determine your tire pressures (likely different front to rear) from their charts. Then you can correctly set your tire pressure.
Getting It Weighed
Weighing by wheel position is offered at many RV rallies. One group that offers this service is RVSEF
(Recreation Vehicle Safety Education Foundation). The actual weighing takes about 15 minutes. They will discuss any need for rebalancing your load and show you how to calculate your correct tire pressure settings. Most truck stops do not offer individual wheel position weighing.
An excellent place for getting your RV weighed by wheel position is provided by Dick Lorntson. Call him at…
Precision Frame & Alignment, Inc.
Elk River, MN
Dick is a vendor at numerous RV rallies and shows, runs his company just north of Minneapolis, and is one of the largest Koni shock dealers in the USA. Best of all, Dick wrote some of the articles in this website under the RV Topic of “Frame and Below.”
Suppose you have it weighed, set your calculated tire pressure, take that trip, return, and repack your RV—i.e., move stuff around, remove things you didn’t use, and put it some new things. Do you have to get it weighed again? Maybe. Hopefully, you have a good “feel” for load balancing from your first weighing, use this as a “best guess” when repacking. Roughly keep track of what you take out and what you replace
it with and you will be able to keep that accurate balance within reason.
Weighing every year is pretty good practice, too, especially if you decide to take your horseshoe collection with you on just some of those trips. The rule of thumb is get it weighed whenever you make a radical change in your load.
Correct tire pressure will lengthen the life of your tires and make your driving easier. Under-inflated tires will wear out faster, decrease fuel economy, and are more prone to failure. Oh well, it’s only money.