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Written by Jim Reeves

It’s not the RV tire we ride on… it’s the pocket of air inside… it holds us up and gets us down the road.

RV Tires are probably more exposed to the elements than any other part of our xcKxR=0 bv989=0 running gear. When you think about it, everything on our Motorhome comes in contact with sun, air and water. Our tires not only have to deal the deteriorating effects of these three elements, they also are making contact with a hard road surface, and anything laying on it. Yet, how much do we think about what is good for our tires, and what can we do to prolong their useful life? Do we understand the science behind our modern pneumatic tires?

If we were to better understand how our RV tires are made, would this information allow us to get a longer service life out of them? I believe that we would… and here’s why. But first a question. Have you ever wondered why it is that we have to cover the RV tires or they seem to rot away? Yet, we can leave our cars out in the sun every day, and they appear not to suffer that same type of drying and cracking that the average RV tire develops? I am thinking that the answer to these questions has to do with two things:

1. The two Key elements that go into the making of a tire.

Our modern RV tire contains various emollients and waxes that protect their sidewalls against the effects of ozone contamination, and carbon black that offers protection against UV damage. The manufacturers of our modern RV tires came to understand as early as 1910, when the B. F. Goodrich Company started adding carbon black to the rubber compound, that there was a need to protect the rubber tire from UV (ultra violet light). This carbon black barrier must be reapplied periodically or our RV tires become susceptible to UV damage.

2. The working conditions that the tire is designed to operate in.

Our RV tires are designed to roll down the road. If they are used in this manner and kept clean, sidewall deterioration becomes less of a concern. This motion, of rolling down the road, allows the wax and emollients to work its way up to the surface of the tire, and offers protection against ozone contamination.

It seems there are three things that will help prevent UV and ozone damage.

1. Keep the tire clean

Like just about everything else we have, if you keep it clean it will last longer. This is something that is easily overlooked, but heavy buildups of mud, sand or dirt act as an abrasive that prevents the waxing process designed to combat ozone destruction. Using mild soap and water with a soft brush on a regular basis will remove a fair amount ozone buildup along with the dirt and grime.

2. Flexing, or using the tire.

This action enhances waxing. This action occurs when we use our RVs. This tire rotation process causes an expansion and contraction motion, that allows a slow wax distribution. This distribution will, in turn, combat ozone oxidation that, if left unchecked, will result in the drying and cracking of the sidewall on your tire.

3. Apply a carbon black component to your tires.

After you have your RV tires clean, you will want to apply a carbon black product like 303 Aerospace Protectant. As far as I know, this is the only product that will work as advertised in combating UV.

It matters what you put on your tire:

Another thing to consider is the fact that any tire dressing that contains petroleum products, alcohol, and/or silicone materials may further damage the tire due to a possible chemical reaction with the antioxidant material in the tire.

These two additives, carbon black and wax, will protect an RV tire from premature drying and cracking.

However, as I stated above, when a tire is not used, this wax additive will lose its effectiveness.

It works like this… according to Doug Jones, Michelin Tire Product Engineer, Ozone is the principal enemy of uncovered RV 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 form a 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. The flexing of a tire will naturally bring wax to the surface on a constant basis. This in done during normal use. RV tires will rot and crack because they sit stationary for long periods of time, and this inaction results in less wax working its way to the surface. Automobile tires have a tendency not to rot because they are more often in constant use. This rotting and cracking phenomenon is an important area of consideration, because, most of us will never wear our RV tires out.

Now we know that we should exercise our RV tires, keep them covered and clean, and put 303 Aerospace Protectant on them.

Unless, we drive them with low pressure, or with alignment issues, they will usually have good tread on them when they are replaced.

For the record, Michelin Tires recommend that:

If the cracks are less than 1/32 deep, the tire is O.K. to run. Between 1/32 and 2/32, the tire is suspect and should be examined by your Michelin tire dealer. If the cracks are over 2/32, the tire should be replace immediately.

What does it mean when we notice unusual wear patterns on a set of RV tires?

Well, by watching how your RV tires wear, and if you learn what the different wear patterns are, you can use this information to learn how other parts of your rig’s health is doing. Such as front end alignment and shock absorber issues. You should inspect your RV tires often… once a week isn’t to often if the tire is in use. You are doing this inspection because you want to detect any early warning signs of mechanical trouble. Trouble undetected can shorten your RV tire’s expected life… and that, my friend, is just throwing money away. Trouble detected can give you clues to other areas of your RV that may need attention.

There are three steps to a complete inspection.

1. Feel the tread by hand to detect a wear pattern such as feathering

2. Examine all six or more of your RV tires

3. Check your tread depth with an analog or digital tread gauge.

Here are some descriptions that will help you understand how tire wear relates to suspension issues.

Wear Indicator

All tires made since 1968 have built-in tread wear indicator bars. When tire use degrades the tread depth to 1/16 (1.5mm), smooth 1/2 (13mm) bands seems to rise toward the surface. This indicates that these tires should be replaced. Many states have laws making this replacement mandatory

Over inflation

When air pressure in a tire is consistently too high, you will see a condition that shows excessive tread wear on the center treads. A rarer circumstance that can cause this condition is when someone puts seriously over sized tires on too small of a rim. These situations result in the center area of the tread being pushed out and wearing prematurely.

Under inflation

If a tire is under inflated, the outside treads will wear prematurely due to unequal pressure across the tread width. In essence, when there is not enough air to push the center of the tire to its proper position, the tire is no longer riding on an air bubble. It is by default resting on the sidewalls, causing outside tread wear. If air pressure is consistently checked and is found to be correct, this condition would indicate a bent steering component (Causes an incorrect toe-in or toe-out position resulting in abnormal handling characteristics when turning) that could be an issue. This could also show the need for a wheel alignment.

Feathered Wear

When you experience a situation where the tread rib becomes slightly rounded on one edge, and a There is a sharp edge on the opposite side of the tread, you have what is referred to as feathering. This is usually caused by a tow-in setting that can be corrected with a proper adjustment. On occasion when the toe-in is set correctly, and you are still experience this feathering condition. This would indicate that you have deteriorated bushing in the front suspension. This causes a shifting wheel alignment when your Motorhome is moving down the road.

Camber Wear

You can always tell when you are due for a wheel alignment when either the outer or inner rib (tread) wears faster the rest of the tire. This referred to as being out of camber, or it is sometimes referred to as a one side wear. This is due to excessive camber in your front suspension. It will cause the wheel (tire) to lean either to the inside, or outside. This will, of course, put an unequal load on one side of your tire. Although alignment issues would be your first suspicion, there could be a more complicated cause like weak springs, worn out control bushings, or worn ball joints. If it is an alignment problem, it will require adjustments to be made. The key to proper alignment is to make sure you have your rig fully loaded the way you would normally drive the thing.

Spotty/Chopped Wear

This is also called cupping. Worn suspension parts that connect to the wheel are usually causing this pattern of cupping. These are scalloped, or dips, that appear universally around the edge of a tire. This can happen on either edge. Usually alignment will not fix the problem. It will require the replacement of one or more of the following components: a ball joint, shock absorber, springs, bushings and etc.

On occasion, you can have bent suspension components creating this type of cupping. The solution to this problem would be replacement of any faulty part/s. Sometimes the tire can be saved if it is rotated to a different location on your rig. Wheel balance issues show a little different pattern. It will create a larger bald spot between the outside and center of the tread.

Dual Kissing

When two RV tires in a dual configuration touch, this is referred to as dual kissing. Under normal circumstances duels will not kiss and you would not have a problem. However, it can easily happen when one or more of the dual RV tires are low in air pressure. Simply put if you do not have enough air in the things, they will squat down and their sidewalls will spread. If they spread enough and touch, you have heating issues that will eventually break down the sidewall and cause a blow-out. This would be called a type of fatigue rupture.

This condition may be caused by more than one factor resulting in improper mounting, incorrect dual spacing, under inflation, and casing growth. In this last case, the fabric casing cords of the tire actually stretch and expand, causing the tire to touch or kiss, under load at the contact patch.

Fatigue Rupture

Fatigue ruptures can occur if you do not pay attention to your GVWR (Gross Vehicle Weight Rating). This condition is sometimes called a zipper rip. Bottom line, if you stress your sidewall beyond their design parameters through an overloaded or under inflated condition, you will create an effect that breaks down the steel casing cords. This whole thing acts like a chain reaction. First one cord breaks which adds additional stress to the adjacent cords and so on until a rupture occurs in the sidewall. Another area that can cause this zipper rip is improper tire blocking (Improperly leveling of your rig).

Proper Leveling Techniques

Leveling of the rig is something that we are all going to have to do on occasion, some of us whenever we go out. It just depends. Some places are level, and some are not. If you have hydraulic levelers, life is easy. For the rest of us, we have to use leveling block of some sort. The challenge is to be able to put your entire tire on these blocks. If you do not, you are running the risk of tire damage.

The thing to avoid is having your tires hang over the edge of the blocking material. You want to use proper blocks that will support your RV tires evenly across the tread width. You do not want to stick a 2+4 under each tire and call it quits… this will break down your steel belts and open up the possibility for blow-out.

Tire Rotation

In a perfect world, you would have no need to rotate your tires if you constantly kept the perfect air pressure and alignment. But, as we have noticed, this is not a perfect world… so we must rotate tires to get their best wear. Because we do have alignment, under/over inflation issues and free rolling wear problems. It is best if we were to follow our manufacturer’s rotation policy. It is a good idea to include your spare tire in this rotation process. Remember, tires like exercise.

Radial tire should be rotated front to back due to issues with the steel belts. It seems that they like to roll in only one direction. If you reverse them, these steel belts start to break down.

Buying New Tires

Essentially, if you are satisfied with the tires you have, then it is a simple matter to just replace them. However, not all tires are equal, and there may be something out there that would suit your needs better. You want to pay attention to whether or not you should buy a 60,000 mile tire if your last set rotted out after 5 years and 35,000 miles. This is almost a totally subjective decision. At any rate, if you replace your tires pays attention to sizing. If you go with a bigger or smaller tire, you may be asking for trouble.

Some things to look at are load rating and gross over sizing. You should know how much your rig actually weighs. So you want to make sure that any new tire replacement is rated for the load you are carrying. A good deal on a tire may not be so, if it is underrated for your needs. This sets up a scenario for all types of problems. Over sizing a tire becomes a problem when your new big tire surpasses the rim size. This means that your rim and tire are no longer in sync. This will give you odd wear patterns and a possible dual kissing issue.

One last question… how do you know just how much weight you can put on your tires specifically?

When you read the fine print on the GVWR, you will notice that refers to maximum weight.

If we are not running around with maximum weight on our vehicles, we should be able to let some air out of our tires! The question is, how much… and why would you want to? Well, we want to let air out if we do not need it, because, maximum air pressure could result in a very rough ride.

This is not only tough on the passengers, but it stresses the drive-train as well. This is not difficult to figure out. However, there are just a few things you need to pay attention to if you are going to start reducing air pressure. First of all you must keep air pressure constant on each axle. To determine air pressure for dual tires, with uneven weight on the axle, adjust the air pressure for all tires on that axle for the heaviest side. To match air pressure load with tire size you can go to the BF Goodrich site and match your tire size and then you will see what the limits are with tire pressure and load capacity. You will note that they a cap at a recommended speed of less than 65 mph.