Tire Care

The rubber around the wheels requires attention if motorhomes are to roll safely down the road.

By Jim Brightly, F358406
November 2015

A tire blowout on a motorhome can be catastrophic. At the very least, it can be a costly, trip-killing, wide-awake nightmare. Even worse, it could total the coach or injure the occupants. So, you want to do everything possible to protect your coach’s tires and prolong their life.

Unfortunately, tires are the most vulnerable component on an RV. With some basic knowledge about tire maintenance, though, you can reduce the likelihood of a serious accident and travel many thousands of trouble-free miles on a set of tires. In fact, if your motorhome is working as designed and your annual mileage is anywhere near the average, your tires will age out before they wear out.

Tire Failures

First, it’s important to understand how most tires fail. According to Goodyear Tire & Rubber Co. engineers, obstructions (nails, sharp objects, curbing, etc.) are the major causes of tire damage. However, many tire failures are caused by progressive wear and tear. As an overloaded or underinflated tire rolls down the highway, it suffers internal damage that is invisible during a casual tire inspection. When the accumulated deterioration exceeds the design limits, a tire failure results. And tires, of course, do not heal themselves, so once they are damaged as a result of improper inflation, reinflating them to the correct pressure will not repair the damage and may not prevent eventual failure.

If you do 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! The recommendation of tire maker Michelin: Briefly push the accelerator to the floor to regain momentum in the direction you are going, and then gently take your foot off of 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). Slow the coach down, without the engine brake or the service brakes, to 10-15 mph before pulling off the road. For more information about these techniques, watch the video on Michelin’s website, www.michelinrvtires.com.

If you carry a spare tire, a service truck summoned via your cell phone can get you back on the road, assuming there’s no body damage to the coach. If you don’t have the capability to carry a spare — and many of today’s mobile mansions do not — you’ll either need a service truck that can bring you a new tire or you’ll have to be towed to a tire store for a replacement. (And being towed to a store isn’t a good option if the failed tire is a dual, because towing at a speed of 5 mph or more causes the remaining tire to operate at almost 100 percent overload, which will result in that tire needing to be replaced at well.) If the original rim wasn’t damaged by the blowout’s aftermath, it can be used with the new tire. Even if you have a spare, you will want to find a replacement tire as soon as possible.

Weigh The RV

Your motorhome’s weight plays a huge role in determining the longevity of the vehicle and its tires. An overloaded coach can cause axle bearings and brakes to fail prematurely, wear out the brakes more quickly, allow unsafe swaying in crosswinds or on curves, increase driver fatigue, and cause the suspension to sag by increasing wear on its components. Even the transmission and driveshaft U-joints can be affected by too much weight. What’s more, both ride quality and tire life are diminished when weight is distributed improperly and heavy items shift around while you drive. Therefore, before buying a new or used motorhome, you should weigh it. And don’t stop there. Weigh it at least once a year. It is the motorhome owner’s responsibility to know the loaded weight of the coach and — if you tow — the combination weight of the coach and towable.

The motorhome’s gross vehicle weight (GVW) should be determined with the motorhome fully loaded, including fuel, propane, water, personal items, and the usual number of people and pets. The gross weight shouldn’t exceed the gross vehicle weight rating (GVWR) assigned to the vehicle by the manufacturer. Exceeding this limit will accelerate wear on the coach’s driveline components and increase the risk to your safety. The Recreation Vehicle Safety & Education Foundation (RVSEF) weighs motorhomes at events around the country, including at FMCA Family Reunions and some area rallies. The schedule is posted on the RVSEF Web site, www.rvsafety.com.

RVSEF equipment can weigh a motorhome at each wheel position. That’s important, because even a coach that is under its GVWR might still have an overloaded tire. And that’s where proper weight distribution comes into play. Consider the locations of appliances when you’re filling the cabinets and storage compartments. Also consider that a feature such as a galley slideout can make one side of a motorhome considerably heavier than the other. Use this knowledge to distribute the movable weight properly from side to side as well as from front to back. Try to store heavier items as low as possible. In addition, everything should be situated so there’s no shifting while traveling.

An alternative means of weighing a motorhome is to use the segmented scales sometimes available at modern truck stops. Most of these scales are large enough to accommodate a coach and towable at the same time, and each axle is weighed separately. (You get a printout showing the individual weights of all the axles on the coach and the towable.) This isn’t as good as individual wheel weights, but it’s better than moving the coach back and forth on a single scale. Most Pilot Flying J and Love’s truck stop locations, which are highlighted in the FMCA North American Road Atlas and Travel Guide, have scales.

Other options for weighing a motorhome might be found in the “Public Scales” section of business telephone directories. You’ll also find scales at many public dump sites, moving companies, recyclers, etc. Ask for three weights: front axle, total, and rear axle. If the scale can’t provide individual axle weights, you’ll have to weigh them separately. As you pull the coach forward, stop with just the front wheels on the scale, and weigh. Then, move forward until both axles — or all three if you have a tag axle — are on the scale, and stop and weigh. Finally, pull forward until just the rear axle or axles are on the scale, and weigh. Don’t worry if the separate axle weights don’t add up to the total weight; for those to match, you’d have to know exactly where your motorhome’s fore-and-aft balance point is. (Imagine a child’s teeter-totter — if one child moves closer to the other, the balance point changes. The same principle applies.)

Follow the tire manufacturer’s recommendations for tire pressure and load range. The inflation pressure should be the same on all tires on the same axle, based on the heavier wheel position. When you check the tires’ sidewalls, you’ll find two weights listed: single and dual. Make sure the actual axle weights are less than these limits. If an overload condition exists, you’ll have to remove and/or relocate the motorhome’s cargo.

Inflation Check

For a tire to do its job, it must retain its proper shape, or profile. And so, to benefit from the engineering that went into your tires, you must maintain the recommended inflation pressure. Failure to do so may result in accelerated and uneven tread wear, improper vehicle handling, and excessive heat buildup.

Too little air pressure will cause a tire to flex too much, resulting in overheating and stress that can lead to premature failure. Too much air also causes problems, because an overinflated tire has less surface area in contact with the road. And that makes for longer braking distances, especially on wet surfaces.

To check air pressure, use an inflation gauge that can read at least 50 percent more than the expected inflation measurement. You can ensure the gauge is calibrated correctly by taking it to a tire dealer or fleet truck maintenance shop to be checked with a master gauge.

The motorhome’s certification label or owners manual indicates the recommended tire inflation pressures when each axle is loaded to its gross axle weight rating (GAWR). However, since motorhomes can be configured and loaded in many different ways, the proper inflation pressure should be determined by actual tire loads. Those loads are determined by physically weighing the vehicle. The weights will change from trip to trip, depending on how the coach is loaded.

Check your tires’ air pressures at least once a month, before each trip, and 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 one mile. Heat generated during driving increases the air pressure above the proper cold-inflation level. This is normal, so never “bleed” air from a hot tire, since that could result in dangerous underinflation.

You might consider buying one of the tire pressure monitoring systems that are becoming more prevalent. New cars and SUVs come from the factory with onboard systems, and some motorhomes are also being equipped at the manufacturer. Sensors in the valve stem of each tire communicate via radio-frequency (RF) technology with a dash-mounted monitor. If you tow a car or SUV with your motorhome, you might wish to purchase a 10-sensor system to monitor all 10 tires. The August 2015 issue of FMC included an article about tire monitoring systems. Or check ads in FMC for suppliers.

In dual-tire setups, it may be difficult to check the air pressures of the inside tires. 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, as well as lower air circulation and crowned road surfaces (which can cause inside dual tires to support more of the load than the outside dual tires).

Many tire shops now are offering to fill tires with nitrogen. Nitrogen molecules are larger than oxygen molecules, so nitrogen is less likely to seep out of a tire than air. But some studies have indicated the advantages are minimal, and many RVers don’t think it’s worth the fuss to switch.

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 do inexpensive plastic caps. It’s good practice to install a new valve assembly whenever a tire is replaced.

Remember, too, that tires wear out faster when subjected to high speeds, hard cornering, rapid starts, sudden stops, and frequent driving on poorly maintained surfaces, although a motorhome rarely encounters these conditions. Potholes and rocks or other objects can damage tires and cause wheel misalignment. (Again, that’s not likely to happen to the heavy-duty components on a motorhome, but your towable may not be so heavy-duty.) Proceed carefully on such surfaces. Before driving at normal or highway speeds, examine your tires for any damage, such as cuts or penetrations.

When a tire is losing air, an expert must remove it from the wheel for a complete internal inspection to ensure it is not damaged. Tires driven even short distances while underinflated by 20 percent or more may be damaged beyond repair.

Punctures up to 1/4-inch in diameter, when confined to the tread, can 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 an unacceptable puncture repair on any highway tire.) Some punctures may make the tire nonrepairable. To be considered a permanent repair, the repair material — for example, a “combination patch and plug” repair — must seal the inner liner and fill the injury. Never use a tube in a tubeless tire as a substitute for a proper repair.

Aging Out

Regardless of usage, tires don’t last forever. Tires should be inspected regularly for excessive or irregular tread wear, bulges, aging, fabric breaks, cuts, or other damages. Remove any nails, stones, glass, etc., embedded in the tread to prevent damage. Normal, natural aging of a tire, as well as the sun’s ultraviolet rays and 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.

If the sidewall looks normal, examine the tread. Wear bars, which look like narrow strips of smooth rubber across the tread, will appear when 2/32 of an inch of tread remains. The appearance of wear bars means the tire needs to be replaced right now. On vehicles with 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, you may want to replace your tires before that to improve traction or vehicle handling. Check tread depth at the beginning of each travel season using a tread-depth gauge, which is available at most large tire outlets.

Each tire’s “birthdate” is molded into one side of the tire. (If the tire is mounted with the date facing inward, you’ll have to crawl under the coach to see it.) Look for a string of characters that begins with “DOT” and ends with four digits. The first of those two digits identify the week the tire was manufactured, starting with week “01” in January, and the last two digits denote the year. So, for example, a tire produced in the 24th week (June) of 2013 would be labeled 2413.

The two major players in the motorhome tire market are Goodyear and Michelin. Tire care guides from both companies note that age cannot be the sole determining factor as to when motorhome tires should be replaced. Many variables have an impact, including usage issues (such as load, speed, inflation pressure, miles traveled per year, and maintenance), storage practices, and weather conditions. Goodyear (www.goodyearrvtires.com) notes that many RV owners replace tires when the manufacturer’s workmanship and material warranty expires. Michelin makes the following recommendations:

• Motorhome owners should regularly inspect tires and maintain inflation pressures. Owners should note any changes in performance, such as increased noise or vibration, which could be an indication that the tires need to be removed from service to prevent failure.
• Motorhome tires, including spare tires, should be inspected regularly by a qualified tire specialist, such as a tire dealer, who will assess the tire’s suitability for continued service. Tires that have been in use for five years or more should continue to be inspected by a specialist at least annually.
• While most tires will need replacement before they achieve 10 years, it is recommended that any tires in service 10 years or more from the date of manufacture, including spare tires, be replaced with new tires as a simple precaution, even if such tires appear serviceable and even if they have not reached the legal wear limit.
• For tires that were on your motorhome when you bought it new, follow the vehicle manufacturer’s tire replacement recommendations when specified (but not to exceed 10 years).

Storage Tips

Motorhome tires are subjected to a wider variety of conditions than automobile tires. Many coaches, for example, are stored for long periods of time, which can cause tires to dry out and crack faster. Protecting tires from direct sunlight — either with ready-made tire covers or pieces of plywood — slows the aging process.

When motorhomes are out of service for long periods, ideally they should be placed on blocks, not on leveling jacks. Place the blocks under the axles so that the tires bear no load during the storage period. Do not place blocks on the frame, because this could cause the suspension to sag or warp over time. Also ensure that the tire/wheel assemblies are protected from direct sunlight. If you cannot safely lift the coach, inflate all the tires to the pressure indicated on the sidewalls and park the tires on plywood or heavy-duty cardboard — not directly on concrete or asphalt. If you store the coach on plywood or wood blocks, be sure that the entire weight-bearing surfaces of all tires are on the wood and that all surfaces are bearing weight equally; no portion of a tire should be off the wood. (This is also important when the tires are on leveling blocks while traveling.)

Because inflation pressure will fluctuate with surrounding temperatures, a slight, gradual air loss will typically occur over extended periods. (Using nitrogen may slow this air loss.) Before returning the coach to service, be sure to inflate the tires, including the spare, to operating pressures. Remember to inflate all tires on the same axle to the same pressure. Make sure the spare tire is inflated to the higher pressure; you can always let air out if it should need to be placed on the axle with the lower pressure.

Before storing your motorhome, clean the tires using plain, clean water and a mild soap; rinse thoroughly when finished. Do not use chemicals or cleaners that contain silicone or petroleum products.

If you remove your tires from the RV while it’s in storage, store them in an area that is clean, cool, dry, dark, well-ventilated, and away from smog and electric generators. Tires should be stored so that those at the bottom of a stack retain their shape. If stored outdoors, tires should be protected with an opaque waterproof covering.

Seminars And More

More information about RV tires can be obtained by attending seminars at FMCA Family Reunions and area rallies. Also, an “RV Safety Training” CD/DVD package is available for $29.95 from the Recreation Vehicle Safety & Education Foundation (RVSEF). Subjects covered include towing, personal safety, weight, tires, propane, fire, driving, electrical, and motor fuels. According to RVSEF, some insurance companies offer discounts to motorhome owners who do any of the following: take a written test after completing the CD/DVD package; complete RVSEF’s Safe Driving program at FMCA Family Reunions or area rallies; or attend RVSEF’s annual conference. Check with your insurance company to determine if a discount applies.

RVSEF also offers an RV Tire Safety video that can be viewed online at www.rvsafety.com; the cost is $19.95.

For RVSEF information, visit www.rvsafety.com or call (321) 453-7673.