Give your motorhome’s tires the proper attention and care they require, and they’ll safely carry you to all of the destinations you’ve dreamed about.
By Jim Brightly, F358406
February 2011
Tires are perhaps the most overlooked and the most vulnerable component on an RV. They also are the most important. They are the vehicle’s contact point with the road, serving as the foundation for your house on wheels. As such, they should be given the same attention and care as the vehicle’s engine, suspension, transmission, and other systems.
Today’s high-tech radial tires are very sophisticated, and with proper care they will give you many miles of excellent performance. With some basic knowledge about the safety aspects of weighing your motorhome, and an understanding of the importance of tire maintenance, you can reduce the likelihood of having a blowout that could lead to a serious accident.
If everything on your motorhome works as it was designed, you should get close to 100,000 miles on a set of tires. In fact, most motorhomers find that they need to replace their tires because of age long before they wear out. However, if you are getting only 50,000 miles or less on your tires before you begin to see signs of wear, your motorhome is probably overloaded or you’ve been running the tires at incorrect pressures.
Getting To Know Your Tires
As you inspect your current tires, or when looking to purchase new tires, one of the first things you should do is to check their age. The “birthdate” of each tire is molded into its sidewall. Find a string of characters that begins with “DOT.” The last four digits indicate the tire’s date of manufacture. The first two digits indicate the number of the week, starting with week “01” in January. The last two digits indicate the year. So, for example, if a tire was produced in the second week of June 2003, the number would be 2403.
So, how old is too old? Tire manufacturers recommend that tires should undergo regular inspection by a qualified tire inspector once they are 5 years old, and should never be used when they are 10 years or older. When checking a tire’s age, should you find that it has only three numbers, replace it immediately. That tire is more than 10 years old and should not be used.
Factors such as load, the tire’s inflation, sun damage, ozone pollutants, your driving speed, and frequency of use represent just a few of the conditions that age a tire. Sun damage can be minimized by covering and protecting the tire from ultraviolet rays using the proper material, but the tire must not be “smothered.” Whatever covering is used should allow the tire to “breathe.” Most RV shops carry tire covers made from the proper material that allow the tires to breathe while in storage.
Tires should be inspected regularly for excessive or irregular tread wear, bulges, aging, fabric breaks, cuts, or other damage. Remove any nails, stones, glass, etc., 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 across the tread, will appear when 2/32-inch of tread remains. The appearance of wear bars means the tire needs to be replaced immediately. On vehicles with gross vehicle weight ratings (GVWR) higher than 10,000 pounds, federal regulations require that tires on the front axle be removed when worn down to 4/32-inch depth; however, you may want to replace your tires prior to wearing down to 4/32-inch to improve traction and vehicle handling. A tread-depth gauge, available at most large tire outlets, can be used to measure tread depth, which 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 motorhomes 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 using compounds that are released within the tire when it heats up from friction on the road. If there is no heat 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. You should check your tires for cracking or other damage before every long trip. Tires that are more than 5 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 or be discarded.
Tire Ratings And Air Pressure
One of the most important issues concerning tires is also the easiest for you to control: tire inflation. Proper tire inflation is a key to protecting the life of tires, especially on motorhomes. Like the relationship between one’s head and one’s hat, tires do more than just support the motorhome. They cushion the vehicle over rough surfaces, carry it to new heights, accelerate the body, and slow the speed. Clearly, your life and those of your fellow travelers are in the “hands” of your tires, and the only way you can reap the rewards from the engineering that went into the tires is to maintain proper inflation.
To fully realize its potential, a tire must have its proper shape or profile to do its job. Low 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 and steering, especially on wet roads, an overinflated tire could cause you to lose control of your vehicle.
Although tire weight ratings may not be found on a tire manufacturer’s data sheets, the manufacturer’s recommended air pressure and (possibly) the tires’ load range are listed there. According to Federal Motor Vehicle Safety Standards, the pressure listed for a tire must be the minimum required to give it sufficient carrying capacity to equal the gross axle weight rating (GAWR), although it can be higher. For tires on a new motorhome, follow the motorhome manufacturer’s recommendations for both pressure and load range. When you check the tires’ sidewalls “” you should use tires of the same size and load range on all wheel positions on each axle “” you’ll find two weights listed there: single and dual. Make sure the actual axle weights are within these weight listings. If an axle is overloaded, remove and/or relocate the motorhome’s cargo. Rarely does the weight placed on each tire on an axle measure to be the same; so, if possible, each individual wheel position on each axle should be weighed and the heavier weight used to determine the pressure for tires on that axle.
Failure to maintain correct inflation pressures may result in accelerated and uneven tread wear, improper vehicle handling, and excessive heat buildup. Walter Cannon, executive director of the Recreation Vehicle Safety & Education Foundation (RVSEF), said that 36 percent of the motorhomes his organization has weighed exceeded the tire ratings, with most of those attributed to underinflation. To make sure you maintain the correct pressure in your tires, check the air pressure regularly with an inflation gauge that is calibrated up to 120 psi. The recommended inflation pressures for your tires are indicated on the certification label or in the vehicle owners manual. However, since motorhomes can be configured and loaded in many different ways, the proper inflation pressure should be determined by finding the actual tire load on each wheel position. The actual loads can be determined only by having each wheel position weighed by a service such as RVSEF. Mr. Cannon said that more than 10 percent of the motorhomes RVSEF has weighed have exceeded a tire rating but did not exceed an axle weight rating. This indicates that it is possible for a tire to be overloaded even though the axle weight is under the GAWR for the vehicle.
Once you determine what the highest tire position weight is on an axle, set all tires on the same axle to the same pressure. Although this may cause a difference in the tire patch should your motorhome be significantly heavier on one side, there are other considerations, such as spring rate, that dictate the same pressure. (The ultimate solution is to balance your coach so that each tire on each axle is carrying the same load.)
Check your tires’ air pressures at least once a month, before every trip, and on each morning that you’ll be driving during a trip. Inflation pressures should be checked when the tires are cold “” that is, before they have been driven. 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 pressures be maintained, because the inside dual tires are subjected to higher heat exposure (from brakes) than the outer tires; less 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 plastic caps. Installing a new valve assembly is a good practice whenever a tire is replaced.
Tire Inspection And Repair
When a tire is losing air, it must be removed from the wheel by an expert for a complete internal inspection to be sure it is not damaged. Tires driven even short distances while severely underinflated may be damaged beyond repair.
Punctures up to ¼-inch in diameter, when confined to the tread, may be repaired by trained personnel. 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 not an acceptable puncture repair on a motorhome tire. Some punctures may make the tire nonrepairable. The repair material used “” for example, a combination patch and plug repair “” must seal the inner liner and fill the damaged area to be considered a permanent repair. Never use a tube in a tubeless tire as a substitute for a proper repair.
It is also important to understand how most tires fail. According to Goodyear engineers, obstructions (nails, sharp objects, curbing, etc.) are the major causes for tire damage. However, many tire failures are caused by progressive damage. Each mile a tire rolls down the highway overloaded or underinflated, it may suffer internal damage, something not visible during a casual tire inspection. The day that the tire fails, you may be traveling with little cargo or not moving at all! The tire simply reaches 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 have suffered damage as a result of being used while underinflated, inflating them to the correct pressure may not prevent eventual failure.
Remember, tires will wear out faster when subjected to high speeds as well as hard cornering, rapid starts, sudden stops, and frequent driving on surfaces that are in poor condition. Surfaces with holes and rocks or other objects can damage tires and cause wheel misalignment. When you drive on such surfaces, proceed slowly and carefully. Before driving at normal or highway speeds, examine your tires for any damage, such as cuts or penetrations.
Should you experience a tire blowout when driving, you better have your seatbelt on, because it can be a wild and bumpy ride. Your first reaction may be to apply the brakes “” but don’t! Michelin Tire Company recommends briefly stabbing the accelerator to the floor 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, gradually move into the far right lane. As soon as it’s safe, turn off the engine brake (if it’s on) and turn on your emergency flashers (to let traffic around you know that something is amiss). If possible, allow the motorhome to slow without using the engine brake or applying the service brakes until it is moving only 10 mph to 15 mph before pulling off the road surface.
Out-Of-Service Tire Care
When you take your motorhome out of service for an extended period of time, one storage method involves placing it on blocks or stationary jacks “” not on its leveling jacks. Place the blocks under the axles so the tires bear no load during the storage period. But do not put the jacks under the frame, because 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. Other tire manufacturers may have different recommendations, so check with the manufacturer of your particular tires about storage recommendations.
In any case, because inflation pressure will fluctuate with surrounding temperatures, a slight, gradual air loss will typically occur over extended periods (using nitrogen inflation will slow this air loss). Be sure to inflate the tires, including the spare, to operating pressures before returning the motorhome to service. Remember, inflate all tires on the same axle to the same pressure, and make sure the spare tire is inflated to the highest pressure used for your tires “” you can always let air out of a tire should it need to be placed on an axle that requires lower pressure.
If you remove your tires from the motorhome while it’s in storage, store them in an area that is clean, cool, dry, dark, and well-ventilated with circulating air. Tires should be stored so that the tires at the bottom of a stack retain their shape. If outdoors, protect the tires with an opaque waterproof covering.
As you can see, making sure your motorhome tires are in good operating condition requires regular inspection, some light maintenance, and acute attention to the inflation pressures used. Perform these three tasks and you will reduce the chances of having tire problems while traveling.