A motorhome’s weight, the distribution of its cargo, and its tires all play a role in your well-being while on the road.
By Jim Brightly
According to John Anderson, who founded the Recreation Vehicle Safety Education Foundation (RVSEF) and served as its executive director until he retired this past July, tires probably are the most vulnerable component on an RV relative to weight and overload issues. They also tend to be the most overlooked. Tires provide the contact point between the RV and the road, and they serve several vital functions. They supply traction for moving, stopping, and steering, and cushion the vehicle. With some basic knowledge about the safety aspects of weighing a motorhome and the importance of tire maintenance, he notes that RVers can reduce significantly the likelihood of having a serious accident.
Mr. Anderson, a retired aviator, founded A’Weigh We Go (the precursor of RVSEF) in 1993 as an RV weighing program. It didn’t take Mr. Anderson and his group long to realize the need for more RV weight and tire education, which led to the organization’s weight and tire safety education seminars. Today, RVSEF instructors attend RV events and rallies throughout the United States and Canada, presenting safety seminars and providing RV weighing services. The seminar educates RVers on serious safety issues such as overloaded RVs and poor tire maintenance. The program is credited with bringing weight safety awareness to the industry and has the support of Recreation Vehicle Industry Association (RVIA), FMCA, consumers, dealers, suppliers, and manufacturers. RVSEF uses the data collected from the thousands of RVs its teams have weighed to measure progress in resolving weight safety issues.
When loading your motorhome, you must first think about proper weight distribution. Consider the locations of appliances when you’re filling the cabinets and storage compartments. Use this knowledge to properly distribute the weight from side to side as well as from front to back. When loading, be sure to distribute heavy items evenly throughout, with the heaviest cargo placed as low on the chassis as possible. In addition, everything should be placed in such a fashion that it won’t shift while traveling. Improper weight distribution and heavy items shifting during the trip can have an unfavorable effect on your motorhome’s handling, ride quality, and braking.
Understanding Weight Ratings
The U.S. Department of Transportation requires that manufacturers place a Federal Safety Certification Label (also referred to as a data plate) on all vehicles that will be used on U.S. or Canadian roads. The data plate, commonly found in motorhomes on the driver’s door panel or on a wall in this area, includes the vehicle identification number (VIN); month and year the vehicle was manufactured; type of vehicle; vehicle weight ratings; and rim and tire information.
In addition, RVIA has developed a set of standards that are listed on a weight label included on every RV manufactured by an RVIA member. In motorhomes, the RVIA weight label generally is located inside one of the coach’s cabinets.
Following are several common weight terms that can be found on either the Federal Safety Certification Label or the RVIA weight label. This information also can be found in the vehicle’s owners manual. All motorhome owners should be familiar with these terms and their definitions.
Gross vehicle weight rating (GVWR) is the maximum permissible weight of a fully loaded motorhome as established by the manufacturer. This weight can be found on both the federal data plate and the RVIA weight label.
Gross axle weight rating (GAWR) is the maximum weight an axle can carry. It is determined by taking the lowest applicable combined rating values of the axle, springs, air bags, suspension, and tires. Front and rear axle weight ratings are established by the axle or chassis manufacturer and can be found on the federal data plate.
Gross combination weight rating (GCWR) is the maximum allowable loaded weight of the motorhome and any towed trailer or vehicle. This is the weight that the motorhome’s engine, cooling system, transmission, and differential have been designed to handle. However, it does not mean that the motorhome’s braking system has been designed to accommodate this much weight. The term was borrowed from the trucking industry and assumes that the towed vehicle or trailer has its own braking system.
Unloaded vehicle weight (UVW) is the weight of the motorhome as built at the factory with full fuel, engine oil, and coolants. The UVW does not include cargo, fresh water, LP gas, occupants, or dealer-installed accessories.
Sleeping capacity weight rating (SCWR) is the manufacturer’s designated number of sleeping positions multiplied by 154 pounds (70 kilograms), used as an average per-person weight.
Cargo carrying capacity (CCC) is equal to the GVWR minus the UVW, full fresh water weight (including water heater), full LP-gas weight, and SCWR. In other words, it’s the amount of weight the owner can add after the motorhome is loaded with fresh water, propane, and passengers. It’s good to know the CCC when purchasing a new motorhome, as it tells you approximately how much weight can be added to the coach and still remain within its GVWR. RVIA weight labels on older coaches may use the term net carrying capacity (NCC), which essentially means the same as CCC.
Weighing Your Motorhome
Now that you’re familiar with many of the terms involved in motorhome weight safety, it’s time to discuss how this information can benefit you, your family, and your motorhome. As you should be aware, it is your responsibility to know the loaded weight of your coach and the combination weight of your motorhome and towed vehicle or trailer if you pull one.
Exceeding the motorhome’s weight limitations means that you are asking the vehicle to do more work than it was designed to do. This can result in poor performance, handling and braking concerns, and premature failure of components. Thus, it becomes both a safety and economic issue.
Ideally, a motorhome should be weighed even before you purchase it. This will ensure that the vehicle will meet your particular travel needs. Typical certified scales are designed to provide a total weight or individual axle weights. It is best, however, to obtain individual wheel weights to help ensure that the load is as equally distributed as possible. RVSEF provides individual wheel weights and an analysis as part of its weighing service at FMCA international conventions and most area rallies.
If you are unable to attend an FMCA convention or area rally to have your motorhome weighed by an RVSEF representative, you can take it to a truck stop where it can be weighed for a nominal fee. You also can look in the Yellow Pages under the heading “Scales, Public” for a certified public scale. Scales can be found at many public dump sites, moving companies, recyclers, grain elevators, gravel pits, scrap yards, agricultural products distributors, etc.
When having your motorhome weighed, ask for three weights: front axle, total, and rear axle. As you pull the coach up to be weighed, stop with just the front wheels on the scale. Next, move forward until all wheels are on the scale and stop. Finally, pull forward until just the rear axle(s) is on the scale and stop. Don’t worry if the separate axle weights don’t add up to be the same as your total weight; you’d have to know exactly where your motorhome’s balance point is for these to match precisely. Also, you could try to weigh each corner of the motorhome, but this is almost impossible, since most scales slope downward on the sides for drainage, and the slope throws off the coach’s weight distribution. Finding out the gross vehicle weight and gross axle weights of your motorhome will help you to properly load and distribute the weight in your coach.
When determining a motorhome’s gross vehicle weight, it should be fully loaded when it rolls onto the scale, including fuel, LP gas, water, personal items, and the normal number of people and pets usually carried. The gross vehicle weight shouldn’t exceed the GVWR indicated by the manufacturer. If the weight of the vehicle does exceed the GVWR, the motorhome is overloaded and will show accelerated wear on all driveline components (i.e., tires, axle bearings, suspension, steering, etc.), not to mention the added risk to your family’s personal safety.
Use the accompanying worksheet to help determine whether your motorhome is below the weight limitations established for the vehicle. Copy the figures from the data labels in your motorhome into the second column. Then enter the actual weight figures in the first column and find the differences. If the actual weight per axle is higher than the label figure, that axle is overloaded. If the total weight is higher than the label figure, your vehicle is overloaded. If the combined weight is higher than the label’s GCWR, the motorhome and towable together weigh more than the motorhome was designed to pull.
The second part of the safety equation has to do with your motorhome’s tires. Today’s high-tech radial tires are very sophisticated equipment, and with proper care they will give you many miles of excellent performance. Neglect your tires, however, and you can expect premature wear, poor handling, and an increased risk of failure.
Begin by checking the age of your tires. The “birth date” of each tire is molded into its sidewall. Find a string of characters that begins with “DOT.” The last four digits in this string indicate when the tires were manufactured. The first two digits indicate the number of the week, starting with week “01” at the beginning of January and going to week “52” at the end of December. The last two digits indicate the year. For example, if a tire was produced in the second week of June 2003, the number would be 2403. Prior to the year 2000, the year was indicated by a single digit (for example, “9” for 1999).
How old is too old? As a rule of thumb, the average life of an RV tire is 5 to 7 years. But factors such as load, inflation, sun damage, ozone pollutants, driving speeds, and frequency of use can all affect the life of a tire.
Sun damage can be minimized by covering and protecting the tire from the sun with the proper material, but the tire must not be “smothered.” The covering should allow the tire to “breathe.”
Tires should be inspected regularly for excessive or irregular tread wear, bulges, aging, fabric breaks, cuts, or other damage. Remove any nails, stones, glass, or other foreign objects embedded in the tread to prevent damage. If the sidewall looks normal, without excessive weather checking, examine the tread. Wear bars, which look like narrow strips of smooth rubber, will appear across the tread when 2/32-inch tread remains. The appearance of wear bars means the tire needs to be replaced immediately. On vehicles with a GVWR in excess of 10,000 pounds, federal regulations require that tires on the front axle be removed when worn down to 4/32-inch depth; however, for improved traction and vehicle handling, you may want to replace your tires before the wear becomes that significant. A tread depth gauge, available at most large tire outlets, can be used to measure tread depth. This should be done at the beginning of each travel season.
Motorhome tires are subjected to a greater variety of conditions than tires used in automobile applications. Many coaches are stored for long periods of time. You may not know this, but a tire that is used regularly will have a longer life than one that is not. Tires are constructed with added compounds that are released when heated by road friction and serve to keep the rubber from drying out. If no heat is being generated, these compounds are not released. Therefore, your tires will dry out more quickly when stored.
Normal, natural aging of a tire, as well as ozone in the air, may cause the rubber to crack, especially in the sidewalls. Check your tires for cracking or other damage before every long trip. Tires that are more than five years old or those that show signs of cracking should be inspected regularly by a tire professional to determine whether they should remain in service.
Perhaps the most important issue concerning tire wear and care is under your control: tire inflation. Proper air pressure is a key to protecting the lifetime of tires, especially on motorhomes. Your tires do more than just support your motorhome. They are responsible for accelerating your motorhome, stopping it safely, and cushioning the ride. Clearly, your life and those of your fellow travelers rely on the performance of your tires, and the only way you can reap the rewards from the engineering that went into the tires is to maintain their proper inflation.
To fully realize its potential, a tire must have its proper shape or profile. Too little air pressure will cause it to flex too much, creating overheating and stress, which can lead to premature tire failure. However, too much air can be nearly as dangerous. An overinflated tire has a reduced contact area with the road. When you need good contact on the road for braking, especially on wet roads, an overinflated tire could cause you to lose control of your vehicle.
Failure to maintain correct inflation pressures may result in accelerated and uneven tread wear, improper vehicle handling, and excessive heat buildup. Make sure you maintain the correct pressure in your tires by checking the air pressure regularly with a tire-pressure gauge that is calibrated up to 120 psi. The recommended inflation pressures for your tires are indicated on the Federal Safety Certification Label, or in your owners manual. However, since motorhomes can be configured and loaded in many ways, the proper inflation pressure should be determined by the actual loads put on the tires. These loads can be determined by physically weighing the vehicle and may vary from trip to trip, depending on how the coach is loaded. Check with the manufacturer of your tires to obtain load and inflation tables.
Inflate all tires on a single axle to the same pressure. Although this may cause a difference in the tire patch (the area of tire tread in direct contact with the ground surface), if your coach is significantly heavier on one side, there are other considerations, such as spring rate, that dictate the same pressure. Rather than adjusting the air pressure, the solution should be to balance the weight of your motorhome by redistributing the cargo so each tire on an axle “” and optimally all tires on the coach “” carry the same weight.
Check the air pressure in each tire at least once a month, before each trip, and at the beginning of each traveling day. Inflation pressures should be checked when the tires are cold, before they have been driven one mile. Heat generated during driving increases air pressure above the proper cold inflation pressure. This is normal, so never “bleed” air from a hot tire, since this could result in dangerous underinflation.
It may be difficult to check the air pressures of the inside tires in dual-tire setups. However, it is important that these air pressures be maintained, because the inside dual tires are subjected to higher heat exposure (from brakes) than the outer tires, lower air circulation, and crowned road surfaces (which can cause inside dual tires to support more of the load than the outside dual tires).
Make sure all tire valves and extensions are equipped with valve caps to keep out dirt and moisture. Metal valve caps produce a better and longer-lasting seal than inexpensive plastic caps. Having a new valve assembly installed whenever a tire is replaced is a good practice.
It is also important to understand how most tires fail. According to Goodyear engineers, obstructions (nails, sharp objects, curbing) are the major causes of tire damage. However, many tire failures are caused by progressive damage. Each mile your tire rolls down the highway overloaded or underinflated, it may be suffering internal damage that’s not apparent during a casual tire inspection. The day that the tire fails, you may be traveling empty or not moving at all. The tire simply will reach the point where the damage has exceeded its design limits. It may blow out or shed its tread. Tires do not heal themselves, so if they are damaged due to underinflation, inflating them to the correct pressure may not prevent eventual failure.
If you experience a tire blowout, you better have your seat belt on, because it can be a wild and bumpy ride. Your natural reaction is to apply the brakes “” but don’t do it! Michelin Tire Company recommends briefly pushing the accelerator to the floor (if traffic conditions allow) to regain momentum in the direction you are going and then gently taking your foot off the accelerator. Hold the steering wheel firmly and regain control. If you are on an expressway, move into the far right lane as quickly and safely as possible. Allow your motorhome to slow, without applying the brakes, to 10 to 15 mph before pulling off the road surface.
Taking Care Of Your Tires
Tires will wear out faster when subjected to high speeds, hard cornering, rapid starts, sudden stops, and frequent driving on surfaces that are in poor condition. Road surfaces with holes, rocks, or other objects can damage tires and cause wheel misalignment. When you drive on such surfaces, do so carefully and slowly. Before returning to normal or highway speeds, examine your tires for damage, such as cuts or penetrations.
Should you have a tire that continues to lose air pressure, it must be removed from the wheel by an expert for complete internal inspection to be sure it is not damaged. Tires driven even short distances while severely underinflated can be damaged beyond repair.
Punctures up to 1/4-inch in diameter, when confined to the tread, can be repaired by trained tire technicians. These tires must be removed from the wheel, inspected, and repaired using industry-approved methods, which call for an inside repair kit and a plug (a plug by itself is unacceptable for repairing a puncture on a motorhome tire). Some punctures may be irreparable.
The repair material used “” for example, a combination patch and plug repair “” must seal the inner liner and fill the injury to be considered a permanent repair. Never use a tube in a tubeless tire as a substitute for a proper repair.
When a motorhome is not going to be used for long periods of time, it should be elevated onto blocks “” not leveling jacks. Place the blocks under the axles so that the tires bear no load during the storage period. Do not put the blocks under the frame; this could cause the suspension to sag or warp over a period of time. Also ensure that the tire/wheel assemblies are protected from direct sunlight. Because tire pressure will fluctuate with surrounding temperatures, a slight, gradual air loss typically will occur over extended periods. Be sure to inflate the tires, including the spare, to operating pressure before returning them to service.
If you remove your tires from the motorhome, store them in an area that is clean, cool, dry, dark, and well-ventilated. Tires should be stored so that those at the bottom of a stack retain their shape. If kept outdoors, protect the tires with an opaque waterproof covering.
For more information about RV weight and tire safety, attend an RVSEF seminar at an FMCA international convention or area rally. In addition, FMCA members can purchase the RV Safety Training Program, which includes manuals covering Towing, Personal Safety, Weight, Tires, Propane, Fire, Driving, Electrical, and Motor Fuels, and an accompanying 120-minute video, for $29.95 plus $6.95 for shipping and handling. It is available by calling FMCA at (800) 543-3622 or (513) 474-3622 Monday through Friday between 8:00 a.m. and 5:00 p.m. Eastern Time (ask for the FMCA Store), or may be purchased online at www.fmcastore.com. For more information about RVSEF, including a schedule of upcoming seminars, visit www.rvsafety.org.
Data Label Information
RV Weight Information Worksheet
Actual Weight Weight On Date Plate
Front GAW: Front GAWR:
Rear GAW: Rear GAWR:
Total GVW: Total GVWR:
GCW total including towable: GCWR total: