It seems topics relating to ensuring RV safety are endless. But RV safety efforts are easier to digest when taken in small increments, so, today’s increment will be about RV tires.
According to the Recreation Vehicle Safety & Education Foundation (RVSEF) your RV’s tires are the most vulnerable safety components. Tires and weight are closely interrelated. Knowing how to stay within safe and balanced weight limits is as important as knowing how to drive your RV. Besides, you’ll have peace of mind if you take the time to ensure that your tires are safe.
RV Weight Considerations
To understand the role your choice of tires will play, you need to understand the weight limitations of your RV. All RVs have weight limitations, which can be found in your manual and on the federal data plate on the outside of your RV. The Recreation Vehicle Industry Association standards require member manufacturers to post additional information inside a cabinet door. Some basic information you need to know includes:
GVWR: Gross Vehicle Weight Rating is the maximum weight the vehicle can carry fully loaded with passengers, gear, supplies, fuel, water, propane, including the tongue weight.
GAWR: Gross Axel Weight Rating is the maximum weight each axel can bear, fully loaded and including the axel’s weight.
GCWR: Gross Combination Weight Rating is the maximum allowable combined weight of both the motorhome and its tow (or dinghy.)
UVW: Unloaded Vehicle Weight includes the weight as it leaves the factory including oil, fuel and lubricants, but nothing else.
CCC: Cargo Carrying Capacity is how much you can load into your motorhome, trailer or 5th wheel. To figure this you take the GVWR and subtract UVW, dealer installed accessories, sleeping capacity at 154 lbs/person, the weight of water and LP gas and tongue weight.
The CCC is a critical weight to know so that you don’t overload your RV. Water weighs 8.3 pounds per gallon and propane weighs 4.2 pounds per gallon. Your UVW includes the weight of full tanks of motorhome fuel.
The amount of weight that remains is how much you can add, including people.
RV Tires: General Information
RV tires are specific to its size and carrying capacity. They are marked with the pressure in pounds per square inch (psi) to fill them, the weight they can carry if single or duals, manufacture date, and more.
Check the RVSEF report linked above or watch the downloadable video Things RV Owners Should Know produced by Michelin Tires. This 16-minute video shows where to find weight ratings on your RV and tires, and both cover just about everything you need to know about choosing RV tires.
Both the RVSEF article and the Michelin video have additional information to help ensure that you and your family will have a safe trip including how to weigh your RV. You can save the article using your print to PDF file command or download the video for viewing whenever you need a refresher. Either will help you minimize any tire failure risk before you leave on your trip.
One finding showed that 10 percent of RVs weighed at an RVSEF event exceeded the RV's tire rating, though not their GAWR. We chose to place light truck tires on our Airstream. These tires are a bit heavier duty, and will hold more weight than our Airstream's GVWR. So, while this won't let us add more weight to our Airstream, we know we won’t overload our tires.
Light truck tires also have stronger sidewalls. We’re fine with “C” walls. "D" or "E" walls are stronger, but may give a rougher ride. Not that it matters in a trailer, but do consider this if you have a motorhome, as you’ll be carrying people on those tires. Also, a less cushioned ride might bounce things around inside, or even bounce some cabinets open. We have "E’s" on our tow vehicle, which gives it more stability when passing 18-wheelers, but can be a bit jarring when we stray from the paved roads (happens often with a 4-wheel drive vehicle.)
Tire pressure should always be measured cold. The air heats up as you travel and the temperature can vary with weather, speed, and type of road material, giving inconsistent results. If you need to measure tire pressure during your trip, stop for 20-30 minutes and let your tires cool down.
Also, measure your tire tread. If you have duals, you should have a minimum of 10/32 on the inner wheel and 13/32 on the outer wheel. Check for cracks in the sidewalls. Don’t use chemicals to clean and shine tires because some break down the tire materials. Use graduated chocks rather than squared edge blocks to brace your tires. And rotate tires on a regular basis.
RV Tire Pressure and Weight Limits
You should weigh not only your RV's total weight, but each axel and wheel to be sure your axel weighs the same on each side. Some RVs should weigh less on the steering wheels than the drive wheels. RV weight will affect braking, and how well your RV grips the road. Trailers and 5th wheels should have enough weight on the tongue/hitch to balance the trailer, neither too light nor too heavy on the rear wheels of the tow vehicle.
Knowing your RV's axel weight limits and how much weight is on each tire will help you load your cargo and plan sleeping arrangements so that you don’t overload any tire. Don’t forget to plan for the weight of water when you get to your destination including your hot water tank, and black and gray tanks. RVs can be weighed at any of several weigh stations found at truck stops or DOT checkpoints.
Our choice was to buy tires rated a bit heavier duty than we needed. Not only do they handle well, but our research and assurances from people who have done the same indicate that they will last two to three times longer than tires rated at the minimum acceptable weight and pressure levels.
Even if you manage to travel safely while exceeding your weight limits, be aware that you are putting excessive stress on your RV’s motor, drive train, transmission and mechanical parts. Sooner or later the abuse will take their toll and shorten the life of your RV. Heavy items that shift while you’re moving can affect how your RV handles on the road, and how quickly it slows and stops when braking. So, be good to your RV and yourself by maintaining your tires safely.