RV care and upkeep
Let’s Talk About Your Weight
By By Ron Jones
May 22, 2006, 19:30

Correct tire pressure in motorhomes 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. Just because you regularly check your car’s tire pressures, don’t assume this is similar to motorhomes.

Two factors are used to calculate correct motorhome tire pressure—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 about this. When something (balloon, beach ball, or tire) is inflated, 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 is "loaded"… fresh water, fuel, canned goods, people, clothes, tools, dishes, and the rest of your stuff!

Tire manufacturers provide charts to help 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.

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.

               

Hear how to determine the proper tire pressure for the weight of your RV.

Suppose you have it weighed, set the correct 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. Because you have an excellent "feel" for load balancing from your first weighing, use this as a "best guess" when repacking. Weighing every year is pretty good practice, too, especially if you decide to take your horseshoe collection with you. Get it weighed whenever you make a radical change in your load.

Correct tire pressure will lengthen the life of your tires—under-inflated tires will wear out faster, decrease fuel economy, and are more prone to failure. Oh well, it's only money.

(This suggestion is one of the more than 500 in All the Stuff You Need to Know About RVing (ISBN 156870514-X) by Ronald Jones info@rvstuff.org and Robert Lowe bob@rv-partsplus.com)