In Part 1, we discussed the importance of monitoring RV tire age along with condition. We will conclude this topic by discussing the importance of weighing your rig, as well as some differences in trailer tire types.
For the safety of the RV (and towing vehicle) occupants and other drivers, as well as longevity of the tires, it is fundamentally important to have your RV weighed. This is true whether the coach is a towable or motorized. Many people don’t realize that the inflation pressure stamped on the tire sidewall is not the recommended tire pressure, but rather the maximum safe inflation pressure. In many cases, this pressure is not the appropriate pressure at any given axle position. Also note that in most cases, each axle position will require a different recommended inflation pressure.
Correct inflation pressure depends on many factors, but from a user perspective is primarily a function of tire manufacturer and weight being carried by the tire. In order to gain a full understanding of your RV weight, it is recommended to have a number of measurements taken. I have found the most convenient way to do this is to roll over a DOT highway scale when it is closed. Generally, these scales are left powered on when the scale is not open, and they normally have a large weight readout that can be used by truckers to observe their own weights. However, certified scales can be found at many truck stops, truck yards, commercial transport repair shops, and at public facilities.
Note that weights should be taken with the fuel and fresh water tanks full, holding tanks empty, and standard cargo aboard.
- First, take a weight reading of the entire unit. If you have a motorhome, weigh the entire vehicle by driving it onto the scale. Weigh a trailer without the towing vehicle on the scale.
- Next, weigh the front axle of the motorhome, then the rear axle set (tandem axles can be weighed together).
- Finally, weigh each wheel position separately. For instance, drive only the driver side front axle onto the scale, then the driver side rear axle, then the passenger side front and rear. In the case of a dually vehicle, it is not necessary to weigh each dually separately. Take note of each of these weights.
The weights you have recorded provide a detailed picture of your rig, including total weight (GVW), as well as side-to-side, axle, and wheel loading. In terms of proper inflation pressure, use each wheel position weight to look up recommended air pressure on the tire manufacturers website or literature. Check the tire pressure cold, and maintain the recommended pressure at each axle position (inside/outside dually, as well as tandem or tri-axles).
One final word about tires. Always ensure your tires are the proper type for the application. For instance, if you have a trailer, check to see whether you have LT (light truck) or ST (special trailer) tires. ST and LT tires have different formulations specific to trailer or truck use, the details of which are outside the scope of this article. Although I generally recommend ST tires for trailers, it is not necessarily a bad thing to use LT tires. Talk to your tire dealer and become informed about each type so you may make an informed choice about which to use.
About the Author:
Steve Froese, an avid RV owner, traveler, and Coach-Net member since 2013, is the principal of “A Word to the Wise Technical Communications”, a published RV author, certified RV technician, and licensed Professional Engineer. He frequently collaborates with the “RV Doctor”, Gary Bunzer, and has worked with the RVIA/RVDA as a technical and training writer and consultant. Professionally, he works as a quality engineer and musician. Watch for more of Steve’s work in upcoming Coach-Net publications.
Karl P. UT~ “Kurt from Quality Tire was exceptional. He came and pulled both sets of back tires. The inside tires on both sides of our motor home had 0 pressure. Both Valve stems had been damaged for some reason. He replaced the valve stems on both tires, checked and filled all 6 tires to correct pressure. He was a pleasant and pleasurable person to work with. We were called by Coach-Net several times to make sure everything went as it was supposed to. Thank you to all the Coach-Net Representatives and to Kurt from Quality tire. It took something that was a pain and made it a pleasure.”