Motorhome Tires

And the Three Most Crucial Areas You Need to Consider

By Gary Bunzer

Sure, we see them every day. We know what they are used for. Wee certainly reminded of them when we have to replace one. Heaven forbid we ever have to replace all six at one time. That the kind of ticket that just may require a cosigner. But we look them over quite well. We even kick them from time to time as a genuine outward display that proves we really care about them. We brag to our campground neighbors and RVing buddies just how many miles wee got on ours. Of course they do the same right back to us. We keep them clean. We buy them fancy wheel covers or better yet, expensive chrome wheels. We even squirt a little air into them periodically. There just like car or truck tires except bigger and more expensive, right? Yep, we really know how to care for our RV tires. But do we really?

Fact is, RV tires, especially motorhome tires need extra care and attention. And no, they should not be thought of in the same vein as standard automotive tires. Today technology may allow certain comparisons as to tire manufacture maybe, but because of the relative infrequent use of the typical motorhome tire, care and maintenance must take on a whole new meaning. To cut right to the chase, as mentioned in the sub-heading above, this article will address three specific subjects of misunderstanding and/or problem areas associated with your RV tires. They are:

This article is not to be interpreted as the only concerns you should have regarding your tires. Indeed there are many others such as proper balancing, alignment, caster, camber, etc., but these three areas, when fully understood, will significantly add an extension of life to your tires. Longer life equates to a more palatable cost per mile and the peace of mind of knowing your tires are performing at their optimum.

One important aspect of quality tire care is regular tire inspections. Not the spurious type that is really nothing more than a quick perusal to make sure the inflator valve caps are still there, along with an assertive kick now and then to make sure the tire is not flat. No, to get the most out of your tires, you must regularly inspect each tire for abnormal wear, cuts, abrasions and any screws or nails you may have picked up recently. The latter is especially true if you just had your unit in for service. Unfortunately, some service facilities have a veritable mine field of puncture-producing projectiles that periodically permeate the pavement, (now there a mouthful!). Check each tire closely. Better to find these items in the relative comfort of a home base rather than while on the road.

Close tire scrutiny and the study of wear patterns over time will allow you to easily diagnose many problems associated with caster, camber, alignment, toe-in and inflation pressures. Become a student of tire wear patterns. It just may save you the expense of many unnecessary or premature repairs to equipment in these areas. While using your motorhome, it is recommended to fully examine your tires weekly at the very least. Also perform an inspection before putting your coach into storage if you are not a full-timer. Resolve discrepancies immediately. Okay, uff said about tire inspections, let take a look at those three areas outlined earlier Inflation Pressure Rate

Let start with air pressure. We all know that the maximum inflation rate is molded into the sidewall of all tires. It is a Federal law. Also, most of us know that this number is the maximum amount of air for that size tire at that load range. Likewise, most of us are aware that perhaps our tires may not need that maximum amount. But how many of us know exactly how much air to carry in our tires? Are we fully aware of the dangers of not having the correct amount of air pressure in our tires?

Incorrect inflation pressures can lead to tire failure, handling problems, overheated brakes, shortened tire life and premature breakdown of other related components on the chassis. Any of which may contribute to a disabling delay or even worse, an accident. Don take any chances. Checking the air pressure in your tires should be a weekly task while you are camped, and a daily habit as you travel.

So how much air should go in there anyway? Since all of us pack and use our motorhomes differently, and each tire may have to carry varying loads, there is really no definitive textbook answer to the question of air pressure that will generically fit all applications. Like many things within the RV realm the amount of air required in each tire is unique to that tire as it carries your specific load. Or at the very least, unique to that axle. However, there is a sure-fire way to determine the exact inflation rate for the tires on your motorhome. And it mandates that you have your motorhome properly weighed after it is packed and loaded as if you were traveling the complete traveling weight. Be sure to include all the canned goods, camping gear, fishing poles, etc. Have the fuel tanks and fresh water tank completely full as well as the LP container, but leave the holding tanks empty. Don forget to include all passengers or at least remember to add an average of 150 pounds for each person traveling in the RV.

Many locales around the country have public scales available that can accommodate motorhomes. Some truck stops or auto recycling yards may also have platform-type scales you can use. Moving companies are another resource to call when looking for a set of scales in your area. They may charge a fee for each weight recorded, but knowing your weights is important.

It will be necessary to take five or six different weight measurements in order to correctly analyze your tire pressure requirements. Here how it done. First, drive onto the scale and pull forward until the rear axle and rear tires are still not quite up to the scale. Record this weight for the front axle. Next, pull forward until all tires are on the platform scale. Record this measurement. Now, continue to pull forward until the front tires and axle are just off the forward edge of the scale. Record this weight for the rear axle. Next you will want to weigh each side of the motorhome. Draw an imaginary centerline through the motorhome and position the coach on the platform weighing each side separately. You will need plenty of clearance on either side of the scales in order to obtain an accurate measurement. The sixth measurement is reserved only for those of you who pull a small car, boat or small trailer behind your rig. The Gross Combined Weight, (weight of the motorhome and its contents, plus the weight of the towed vehicle and its contents), will be helpful information for you. Especially when considering or troubleshooting performance, handling, or engine and drive train operations. Here a handy chart that summarizes the weights you will need. You will notice a column for the Manufacturers Rating. This information can be gleaned from your owners manual or from the data plate found inside your motorhome. Fill in the appropriate weights measured during your visit to the scales.

Measurement-Location-Actual -Weight-Mfg.- Rating-Variance (+ or -)

1. Front Axle
2. Gross RV
3. Rear Axle
4. Right Side N/AN/A
5. Left Side N/AN/A
6. Gross Combined (if you tow)
   

With the actual Weight column and the fig. Rating column filled in, now simply do the math to determine how you rack up to the specifications as outlined by the manufacturer. If you appear to be overweight in any area, perhaps moving camping items or stored goods will even things out. Generally, the total weight of measurement number two will be the approximate sum of measurements one and three. Do not be overly concerned if these numbers cannot be reconciled to the single pound. In this case, close is okay.

If you do tow, another optional weight measurement that is handy is the weight of the towed vehicle only the car, the boat, etc., by itself, including all its cargo. This weight added to measurement number two, should be close to the Gross Combined Weight you recorded in measurement number six.

So how does all this relate to air pressure? By knowing what each axle is actually carrying, especially if your right and left side measurements are relatively balanced, you can compare it to the published recommendations and weight restrictions for your size tire, rim and load range. If your right and left side measurements were radically different, rearrange your stowed goods until a more equitable balance is obtained. All tire companies have a chart that details exactly how much air pressure each size tire should be inflated to based on two things; how much weight it is carrying and if it is on a dual rear axle, or a single axle, (front axle or rear tandem). Michelin Tire Corporation has available a Recreational Vehicle Tire Guide that details various inflation rates based on tire size, load range index and weight. (To obtain your free copy of the Michelin booklet, contact the mat the address listed at the end of this article) Speaking of Michelin, look for a brand new tire from them specifically designed for RVs. Called the XRV, it will be available sometime during the second quarter of 1996.

For optimum results the proper air pressure in each tire must be calculated by knowing how much your rig weighs, how it is distributed and how much of that weight is carried by that particular tire. Remember to take air pressure readings on a cold tire only. Leveling and Blocking Techniques

If your motorhome is equipped with automatic levelers or jacks, you are fully aware of the advantages that come with such equipment. One of the most beneficial uses is the help the levelers provide for your tires. By leveling your coach while stopped or camped, you take a lot of the weight off each tire (assuming all jacks are deployed). This simple reduction of weight greatly eases the stresses and loads upon each tire thereby extending the useful life of your tires.

For those of us who do not have the luxury of leveling jacks, we must rely upon the tried and true method of using leveling blocks. Whether we choose the homemade variety or those that are store bought, keep in mind there is a wrong and a right way to use them. A recent stroll through a typical campground revealed some shocking sights. Many RVers were using simple 2X4's as blocking material. Most of us are aware that a typical motorhome tire is much wider than a piece of 2 X 4lumber (actual dimension; 1-1/2" X 3-1/2"). Additionally, this writer witnessed many blocking examples where only the outside dual was blocked to raise that rear corner. Another no-no, especially for radials. Over time, uneven distribution of weight while blocking can damage the steel cables, the casing and especially the sidewall. In some cases, the damage may not be readily visible until after a failure has taken place. Maximum support is mandated in order to avoid warranty discrepancies and premature tire failure. Here a few simple examples provided by the Michelin Technical Group that further exemplifies the correct and incorrect methods.

Figures one and two show the correct method of using wood blocks to support the footprint of a single tire and the rear duals of a typical motorhome. Notice how the boards extend well beyond the actual tire footprints. If additional height is needed for proper leveling of the refrigerator, a progressive set of boards may be used as long as the bottom board is the longest and the widest and the additional boards are progressively shorter. The uppermost board that is in direct contact with the tire still must maintain the full tire footprint, and then some.

Figures three and four show a few examples of how NOT to use blocks to support the weight of the coach. A quick inspection through any campground will probably yield a myriad of additional incorrect methods. It becomes obvious that improper blocking and leveling, over time, will indeed damage even the strongest of sidewalls. By practicing the correct blocking methods and making it a regular campsite habit, you will add many months to the life of your tires. UV/Ozone Damage

The third and final topic for this discussion about your tires pertains to virtually all tires, RV and otherwise. The damage caused by ultraviolet (UV) radiation and ozone exposure virtually effects all tires, or for that matter, anything else made of rubber, vinyls, plastics or fiberglass. Even our skin is not immune to the affects of the damaging ultraviolet rays of the sun. Motorhome tires are more susceptible to this type of damage since they are considered a slow wearing tire. Truth is, many car tires simply wear out before such damage can occur. Generally though, motorhome tires are not driven as far or as often as regular automobile tires over their lifetime. Many motorhome tires spend the majority of their time literally just sitting there absorbing the ozone and UV rays. A typical symptom of ozone or UV damage is the evidence of cracking or weather-checking around the circumference of the sidewall. Here a brief discussion of UV and ozone damage that further explains why this occurs.

Ozone, wee all heard the term, is simply a gas that is in the atmosphere. It is usually more prevalent in industrial areas or heavily polluted areas where a lot of electromagnetic charges may be found free in the air. It can be produced by arc welding equipment or any spark producing motors such as an RV generator. A recent article even suggested that incomplete combustion of LP can produce a variable of carbon monoxide that contributes directly to ozone.

A mutant of sorts, ozone consists of an extra oxygen molecule which is easily attracted to the oxygen in the air and just as easily attaches itself to other oxygen-related chemical compounds such as water and the above mentioned carbon monoxide. Its main detriment to RVers is that it virtually attacks the rubber in the tires and causes brittleness and lack of pliability. The big disadvantage ozone produced cracks in tires cannot be repaired or brought back to life. The tire must be replaced.

Unprotected tires on stored RVs are most susceptible to this kind of rot damage, but all tires are targeted by ozone as well. According to Doug Jones, Michelin Tire Product Engineer, zone is the principal enemy of uncovered tires. One of the ways tire manufacturers combat ozone is by blending ozone resistant rubber compounds during the making of the tire. These special waxes forma protective barrier against the ozone, but in order to keep up the battle, the waxes must be constantly brought to the surface of the tire. This is accomplished naturally by simply putting the tire to use. During the flexing and moving of a tire while you travel, a fresh layer of combative waxes is kept at the surface. Unused tires on stored vehicles do not receive enough exercise to allow the waxes to migrate to the surface and the ozone has a virtual picnic on any exposed area, especially the vulnerable sidewalls.

Ultraviolet light (UV), on the other hand, is produced by the sun and travels in the air as solar radiation. An invisible light, UV is harmful to all rubber, plastics, fiberglass, etc., all of which are common to RVs. The effect of unprotected UV exposure on rubber is similar to that of ozone damage cracking, discoloration and lack of physical mechanical properties. Ever remember seeing rubber window molding on older vehicles that had deteriorated and turned chalky looking and brittle? That UV damage. Because UV rays work in conjunction with ozone in the free air, all tires are susceptible to this type of damage, not just those in high ozone concentrated areas. Ozone and UV rays basically, double-team your tires.

Like the ozone war, tire manufacturers use carbon black during the manufacturing process to combat the effects of UV radiation. As the compound waxes in the tire protect against ozone, so the carbon black protects against UV damage. Carbon black is an UV stabilizer that actually absorbs the damaging rays and coverts them to a simple heat by-product. That the good news. The bad news is that all UV stabilizers are eventually used up during this protection process and must be replenished in order to receive optimum tire life. As a competitive absorber, carbon black eventually loses its ability to protect against the never-ending assault of the UV rays. The other bad news is that there is no such thing as a permanent UV blocker.

So what to be done? How can we get the optimum performance and life out of our tires? Here are a few ideas suggested by virtually every tire manufacturer and retailer;

• Keep your motorhome tires clean. Avoid heavy buildups of mud, sand or dirt.
• Dirt on tires may as an abrasive of sorts that could inhibit the natural wax protection achieved through normal tire flexing and typical use. Also, regular washings with a mild soap, water and a soft brush can remove significant amounts of ozone, especially if you are located in a higher than normal ozone area
• Inspect your tires regularly.
• Inflate your tires to the exact requirements based on weight.
• During short periods of non-use, keep the tires completely covered. Invest in aftermarket tire covers or fashion a set of your own. longer periods of storage, if possible, remove and store the tires separately, completely out of the sun and temperature extremes. you have a spare tire, consider adopting a regular rotation schedule so the spare gets its share of exrcise and flexing. And be sure to keep it covered.
• Practice correct blocking and leveling techniques as outlined in this article. This will avoid unnecessary stresses that lead to premature tire replacement.
• Avoid using, so called, tire treatments that contain petroleum based substances. Any tire dressing that contains alcohol or petrochemicals may, instead of protecting, actually cause and accelerate deterioration and cracking. Some silicone oils found in such products will dissolve the protective wax that protects the tire against the ozone damage. Also, petroleum based tire treatmentscontain no viable UV stabilizers at all, so the tire is left virtually stripped of any ozone protection andmust contend with UV radiation with no replenished stabilizers. Additionally, many tiremanufacturers actually inspect the tire for use of these chemicals, especially in the case of prematuresidewall structural failures in a warranty situation.

But if the carbon black is eventually used up, what is used as a UV stabilizer replenisher? One of the most recommended and effective UV sunscreens for tires is a product called 303 Protectant. Similar to the rating of sunscreens for your skin, 303 has a protective sunscreen rating of 30. It will not remove the protective waxes in the tire and it actually adds to the UV protection by absorbing into the rubber, thereby delivering a set of UV stabilizers in direct replenishment of the depleted carbon black. Regular treatments with 303 along with the above recommendations will indeed extend the life of your motorhome tires. And that, will profoundly effect your wallet in an appreciable way. Remember, RVing is more than a hobby, it a lifestyle!

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Gary Bunzer, known as the RV Doctor to many readers, is a rare breed. He not only knows how to trouble shoot and repair the RV components, he also knows how to teach others through writing articles and giving seminars.