Mark’s RV Toolbox

Something I never leave home without is a quality tire pressure gauge. Like everything else these days’ things are switching from analog to digital. Analog tire pressure gauges were the standard for many years, but advancements in digital technology have improved on that standard. In numerous tests comparing different type gauges digital gauges proved to be the most accurate tested. Regardless of the type of gauge you choose there are high quality and low quality tire gauges available. Buying a cheap digital gauge would be the same as buying a cheap pencil type gauge. I never leave home without this digital tire pressure gauge by Tire Minder .  Here are a few things to keep in mind when it comes to tire pressure gauges:
1) Spend a few more dollars and get a quality pressure gauge.

2) If the gauge will be used for checking dual wheels on a motorhome the chuck end of the gauge should have a dual foot design to make the job much easier.

3) Always select a gauge rated higher than the inflation pressure of the tires you are checking. Applying more pressure than the gauge is rated for can damage the gauge and affect the accuracy. If you over-pressure a gauge have it tested for accuracy. This gauge is rated up to 150 psi.

4) Try not to drop or jar the gauge. Store the gauge in some type of protective covering or case and in an area where it won’t be hit or damaged.

5) Periodically have the gauge tested for accuracy. At a minimum compare it to another quality gauge to see if both read the same, or close to the same pressure.

6) Most importantly, once you purchase a quality pressure gauge use it on a regular basis to check your RV and automobile tires.

Happy RV Learning,

Mark Polk

RV Education 101
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Copyright by Mark Polk owner of RV Education 101

RV Tire Tips - How To Determine Your RV Tire Pressure

RV Tire QUESTION:

Mark, can you tell me the correct pressure that you should inflate a tire to before taking a road trip. My trailer tires say max psi 70lbs. I can't seem to get a straight answer from our local shops, and I want to make sure I don't overheat them. I do know to check them first thing before driving and before the sun hits them. Thanks for any information!

Mark's Answer:

It can be a bit confusing, but I'll try and explain. Tire manufacturers publish tire load and inflation tables for tires they manufacture. In a perfect world you would know what the actual load is being placed on the tires and could go to the load and inflation tables for precise inflation pressure.

Since we know this isn't always practical there are a couple of ways to help determine tire inflation pressure. On the front left corner of the travel trailer you will find a Federal Certification Tag or label. This label displays information on tire inflation pressure, GVWR and GAWR. The tire inflation you see on the label is based on what the trailer weighed when it was built. If no additional weight is placed on tires this inflation pressure is accurate, but we all add weight to the RV when we load it for a trip. The question is how much weight is added and the only answer to that is to have the RV weighed, preferably by individual wheel position.

The inflation pressure molded into the sidewall of the tire is the maximum amount of air pressure you would ever inflate the tire to if a full load was placed on the tire. You can find the tires max load range on the sidewall too.

What this means is, if the trailer tires are not overloaded the inflation pressure (depending on actual weights) is somewhere between what is posted on the certification label and molded in the tire sidewall. In other words in some cases it is possible to increase tire load capacity by increasing the inflation pressure in your tires, but you cannot exceed the maximum pressure specified on the sidewall of the tire. You can usually find load and inflation tables on the internet.

It’s also important that you use the same inflation pressure on both ends of each axle. If you weigh the RV and the tire loads are different on each axle end the load tables might require different inflation pressures. When this happens you need to redistribute the load. If the load can not be redistributed you would inflate both of the tires to that axle to the inflation pressure required for the tire with the heaviest load. Keep in mind that it cannot exceed the max tire pressure molded in the sidewall.

Here are a few general rules for tire inflation I like to use:

• Never pull the trailer with tires inflated to less pressure than required for the load placed on the tires.
•  Never pull the trailer with tires inflated to less pressure than what is on the certification tag, no matter what the load.
•  Never inflate your tires above the maximum pressure shown on the tire sidewalls.

Happy RV Learning,
Mark Polk

RV Education 101
RV University
RV Online Training

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Copyright by Mark Polk owner of RV Education 101

RV Tire Age can result in Tire Failure

Tire failure on RV’s can be extremely dangerous and can cause extensive damage to your RV. There are lots of reasons for tire failure on RV’s, like under inflation, over inflation, overloading and the age of the tires. Today I want to discuss how the age of your RV tires, and exposure to the elements, can lead to tire failure.

Tires are designed and built to be used. The rubber used in tires ages faster when they are not used, so more use results in longer tire life. The problem is lots of RV’s don’t get used that much.

When tires are manufactured compounds are added to help protect the rubber from weather cracking and ozone damage. The problem is the tire needs to be rolling down the road, heating up and flexing for these compounds to work their way to the surface of the tire and protect the rubber from damage. So, when tires sit still, like in storage they start to dry out causing them to age faster.

Weather cracking or checking occurs on all tires when they are exposed to heat and sunlight. This is especially true of the tires sidewall. Ozone in the air and UV rays from the sun shorten the life of your tires. It’s not uncommon to see RV tires with low mileage and plenty of tread that are ruined by the damaging effects of ozone and UV rays. Ozone in the air causes tires to dry rot and deteriorate. UV rays from the sun , and not using the RV make it happen quicker.

You need to inspect your tires for weather checking or cracks in the sidewalls before each trip. Cracks less than 1/32 of an inch deep are ok, but if the cracks are more than 2/32 of an inch deep the tire should be replaced immediately. If you notice damage to the tires and you’re not sure what to do have them inspected by a professional.

This faster aging and weather cracking are why tire manufacturers recommend replacing the tires on RV’s when they are 5 to 6 years old, especially if the RV isn’t used that much.

So how can you tell how old the tires are? All tires manufactured in the United States have a DOT number. The DOT number may be on the inside or outside sidewall. At the end of the DOT number the last three or four digits in identify how old the tire is. Older tires used three digits. The first two identify the week of the year the tire was built and the third identifies the year. Newer tires use four digits. For example 3208 is the 32nd week of the year and 08 is the year 2008. If you question the age of your tires, especially on a used RV, and you can’t find the DOT number have them inspected by a qualified tire center.

Even though there are many other factors that can affect the life of your RV tires you can see that the age of the tires is one of the most important consideration.

Watch a 20/20 report on how the age of tires can result in dangerous tires http://www.youtube.com/watch?v=mDgSk5xWkrI

Now that we know how age and the elements can affect the life of your RV tires what can we do to help extend the life of tires when they’re not being used?

Considering where and how your RV is being stored can add life to your tires. Of course a covered, dry garage is the best scenario, but we know this isn’t always possible.

The first step is to clean the tires. Clean the tires with a mild soap and water. Avoid using tire dressings. Sidewall rubber contains antioxidants and anti-ozones that are designed to work their way to the surface of the rubber to help protect it. Washing tires excessively removes these protective compounds and can age tires prematurely. The same is true of most tire dressing designed to make your tires shine.

Inflate the tires to the recommended inflation pressure on the tire sidewall when in storage.

Avoid storing tires on petroleum based products like asphalt and other heat absorbing surfaces, and avoid storing tires on frozen ground.

If stored outside you should place some type of barrier between the tire and the ground surface. Make sure the blocking is wider than the tires tread and longer than the tires footprint. If tires are not blocked properly and the load distributed evenly the tire sidewalls can be damaged.

Avoid any exposure to heat and sunlight. If the RV is stored outside cover the tires with covers that block out the sun.

The RV should be stored with the least amount of weight on the tires as possible. That means it should be unloaded prior to storage.

You should move the RV every few months help prevent sidewall cracking from the tire sitting in one position for too long.

Following these simple tire storage tips can add life to your RV tires, but keep in mind that tire age and exposure to the elements are leading causes for tire failure. Make sure you know the age of your RV and automobile tires and always inspect your tires for signs of weather cracking before each trip.

For more information on maintaining your RV check out our RV Care & Maintenance DVD

Happy Camping,

Mark Polk

RV Education 101

RV University

RV Tire Tips for Safer RV Trips

It seems as though I talk about tire safety all of the time. The reason I do is because tires are an important safety topic concerning RVers that are often times overlooked.

Just recently I read a newspaper article that summed up just how overlooked tires, in general, are. The article stated, “The Rubber Manufacturers Association found that 29 million drivers believe that tires require no regular maintenance.” This number might be considered small when compared to our current deficit, but it is quite large when you consider 29 million people are driving around the country on tires they don’t know the condition of.

With peak travel season quickly approaching I thought it would be a good time to offer some tire tips for safer trips. These tire tips apply to your automobile as well.

Watch the RV Tire Tips Video

Two of the biggest problems with RVs today are overloading the RV and under inflated tires. With multiple slide-out rooms, large holding tank capacities and the ample amount of storage space available on today’s RVs it’s easy to see why so many are overloaded. We have a natural tendency to fill every nook and cranny of available storage space on our RVs.

Another problem is out of balance loads. You can be within an axle or tire’s load capacity on one end of an axle, and be over capacity on the other axle end. This is a common problem with RVs and many times the cause is poor weight distribution and/or improper loading of the RV. When this happens the tire or tires on the end of the axle that is overloaded are subject to tire failure. The bottom line is overloaded RVs and under inflated tires can be extremely dangerous. The only way to make sure that your RV is not overloaded is to have it weighed.

Weight ratings for RV’s are established by the manufacturer and are based on the weakest link in the chain. When you exceed a weight rating you are overloading one or more components on the RV and risk wearing the component out prematurely or complete failure of the component. In many cases the tires on your RV are the weakest link. Just like the axles on your RV, your tires have load ratings too. The maximum ratings are molded into the side of the tires. Keep in mind these are maximum ratings. The sidewall of the tire shows the maximum load and the inflation pressure for that load. Never set the inflation pressures below the recommendations you find on the vehicle manufacturers placard and do not exceed the maximum inflation pressure ratings found on the tires sidewall.

The tires on your RV are the most vulnerable component affected by overloading the RV. There are numerous reasons for this. First and foremost is when the tires are not inflated properly for the load. Failure to maintain correct tire pressure can result in fast tread wear, uneven wear, poor handling, and excessive heat buildup, which can lead to tire failure.

The only way to correctly measure the inflation pressure in your tires is with a quality inflation pressure gauge. Using your boot, a billie club or a hammer is not accurate, and never depend on your eyes to check tire inflation. There can be as much as 20 PSI difference between tires that look the same to your eye. You need to invest in an accurate inflation pressure gauge. You should get one with a double, angled foot. This makes it much easier to check the outer tire of a dual set.

Check all of your tires on a regular basis and adjust the pressure according to the manufacturer’s recommendation. Never check inflation pressure when the tires are hot. You’ll get a higher-pressure reading and if you let some air out they will be under inflated when they are cold. If you have dual wheels you’ll want to add extension hoses to the valve stems to make the job of checking tire inflation easier. It can be nearly impossible to check the inner dual without extension hoses. The best extension hoses will have stainless steel reinforcement and external braiding for long trouble-free life.

Ozone in the air and UV rays from the sun shorten the life of your tires. It’s not uncommon to see RV tires with low mileage and plenty of tread that are ruined by the damaging effects of ozone and UV rays. Ozone in the air causes tires to dry rot and deteriorate. UV rays from the sun make it happen quicker. This is especially true of the tires sidewall. Inspect your tires for checking or cracks in the sidewalls. If you notice any damage to the tires have them inspected by a professional.

Keep the tires covered with covers that will block out the sunlight when you’re not using your RV. You should also place something like a piece of wood between the ground and the tires. Be sure that whatever you use is larger than the footprint of the tire. No portion of the tire should hang over the edge of the tire block. This can cause internal damage to the tire.

Occasionally washing your tires with soap and water is OK using a soft brush. Sidewall rubber contains antioxidants and anti-ozones that are designed to work their way to the surface of the rubber to protect it. Washing tires or scrubbing excessively removes these protective compounds and can age tires prematurely. The same is true of most tire dressings. Products that contain petroleum, alcohol or silicone are bad for tires.

Tire failure can be extremely dangerous and can cause extensive damage to your RV. There are no
guarantees, but by practicing good tire maintenance you can feel much safer and secure that the weakest link on your RV will do its job while you’re out exploring this wonderful country we live in.

If you would like to learn more about maitaining your RV check out our RV Care & Maintenance DVD

Happy RV Learning,

Mark Polk
RV Education 101
RV University
RV Consumer

Where's the Spare

Why don’t some RV manufacturers include a spare tire with a new RV? Is it a liability issue or a cost issue? I have heard both sides of the story over the years, and it usually depends on what type of a RV you are talking about.

I have owned three towable RV’s and two motorized RV’s. Two of the towable RV’s came with spare tires when I purchased them and I ordered a spare tire as an option on our Class C motorhome, but I could not get a spare for our Class A motorhome.

It seems ridiculous that you buy an RV, designed for traveling all over the country, and the one thing not included is a spare tire. Let’s try to find out why there’s no spare!

It has been rumored that many years ago an RV owner got hurt while changing a tire on his motorhome and that he sued the RV manufacturer. This is supposedly why many motorhome manufacturers opt not to include a spare tire, especially on larger motorhomes.

Admittedly changing a spare tire on a large motorhome is not the same as changing a tire on your automobile. From a liability standpoint the argument is because of the size of the RV and the weight of the tire and wheel it can be dangerous for an individual to attempt changing a tire. Plus you would need to carry some special type of equipment to safely and properly change a tire. I would have to agree, but why not include a spare (without a jack or the other necessary equipment) and have a mandatory warning label stating the dangers of changing a tire along with a recommendation to use a professional road side tire service to change the tire for the owner.

Here is what some RV and chassis manufacturers have to say:

Why doesn't the RV come with a spare tire?

The combined weight of the tire and wheel is approximately 110 pounds. Even if you feel comfortable lifting that amount of weight, other variables pose a problem when it comes to changing an RV tire. You may find yourself on the side of the road in a confined situation, or during the nighttime when it is raining.

Jacking up the side of the RV would be difficult. Leveling jacks are not designed to lift the entire wheel off the ground to change a tire. To change a flat RV tire, it would be necessary to store the correct jacks and jack stands for safety. The next hurdle would be the lug nuts, which are torqued to 500 pounds and difficult to remove. Once removed, and while reinstalling, a tool to properly retorque the lug nuts would be needed. All these necessary tools, combined with the actual spare tire, would take up a considerable amount of space and add additional weight to the RV. Call roadside assistance for tire repair and save yourself the aggravation.

My vehicle doesn’t include a spare tire. Where can I get one and where can I store it?

Most larger motorhomes don't provide a spare for several reasons. Generally, the wheel assembly is too cumbersome and heavy for one person to change alone without risking injury. We'd recommend that, in the case of a flat, you enlist the help of a roadside service crew to fix your flat tire. If you do decide to obtain a spare wheel assembly, contact your dealer for details on ordering one and the proper way to store it.

Now that we know why some motorhome manufacturers don’t include spares why don’t some of the towable manufacturers include spares?

This is where the cost issue comes into play. RV manufacturers look at every penny going in to manufacturing the RV. Not including a spare in the base price of the RV can save money, so they list the spare tire as optional. What this means is when the RV dealer orders the unit they can add a spare or not add a spare. If a dealer is trying to bring a unit in based on price point they limit the options included on the unit. When I was a RV sales manager I included a spare tire on every towable unit just because it made sense and it really wasn’t that expensive.

You still need to consider the safety aspects of changing a tire on a trailer. Even though it’s smaller and lighter than a motorhome tire you still need equipment like a jack, jack stands, lug wrench and torque wrench. In addition to the equipment required, you need to have a basic understanding of how to safely and properly jack the trailer up. But again, if you have a spare you can always call a roadside service to change it for you. If you don’t have a spare you may be stranded in some out of the way place until the tire can be ordered and come in. This could take a couple of days, or longer.

That brings me to how this article came about. We are planning a cross country RV trip this summer and I refuse to go without a spare tire. Our motorhome has 22.5 inch tires with 8 lug rims. When I tried to locate a tire and rim it was difficult to find one. I’m sure I could order one from the manufacturer, but I would be afraid to know what the cost is. We have a good roadside assistance plan so what I decided to do was to just buy the tire itself and if I have a flat the roadside tire service can mount the new tire on the rim. It is less weight to carry and it eliminates the possibility of delays due to ordering and waiting for a tire to come in, if it isn’t in stock.

Regardless of whether or not your RV came with a spare I think it’s a good idea to get one, and I think for safety reasons you are better off having a roadside service plan that will change the tire for you.

What do you think?

Mark Polk

RV Education 101

RV University

Debunking Portable Air Compressors

I think most RVers understand the importance of maintaining proper tire inflation pressure. The problem is if you wait until you’re on the road to check tire pressure the tires are too hot for correct evaluation. Checking the inflation pressure when you stop to refuel doesn’t make sense; you will get higher pressure readings and if you let air out the tires they are underinflated when they are cold. Another problem is when you are at the campground, and you want to check the tire pressure, there is no available air support to do it.

This is why you might want to consider purchasing a portable air compressor. But, air compressors can be confusing to understand, especially if you are trying to find one that is capable of increasing the inflation pressure in large motorhome tires. Let’s start with some air compressor basics.

Air compressors have 3 main ratings associated with them, horsepower (HP), Cubic Feet per Minute (CFM) and Pounds per Square Inch (PSI). Understanding these 3 functions of an air compressor can help us select the right portable air compressor for the job.

We’ll start with horsepower. Unfortunately when it comes to air compressors manufacturers don’t do a great job of explaining it to the consumer, almost to the point some would consider false advertising. Manufacturers tend to over-inflate HP ratings, assuming if the consumer see’s 6 HP advertised, rather than 2 HP, they are more apt to purchase the higher HP rated compressor. This is true in many situations. If you’re a muscle car enthusiast you would definitely consider the HP rating of a vehicle before buying it, right? But if we take a closer look at horsepower, as it relates to air compressors, we can seek out the truth.

Horsepower was invented by an engineer by the name of James Watt. The same watt you think about when buying a light bulb. Watt is used as a measure of electrical and mechanical power. When we apply watts to HP, one HP is equivalent to 746 watts. So if you buy an air compressor rated at 6 HP and it operates on 120 volts it is, in a sense, a false rating. Here is why. If you plug the compressor into a standard 15 amp, 120 volt circuit it would only produce about 2HP (120 volts X 15 amps = 1800 watts).  This is slightly over a 2 horse power rating.

The higher 6 HP rating advertised is commonly referred to as peak HP, similar to a vehicles engine HP rating. The peak HP rating of a vehicle engine is only accurate at a higher RPM range (usually 5000 to 6,000 RPM’s), but rarely do you drive at 5,500 RPM’s. As for the air compressor it would require more amps, from a 240 volt circuit, to produce this peak HP rating.

The Cubic Feet per Minute (CFM) is an important rating when it comes to portable air compressors. CFM is basically a measurement of the rate a compressor can deliver a volume of air. CFM varies with atmospheric pressure. It also varies with the temperature and humidity of the air. Air compressor manufacturers calculate Standard Cubic Feet per Minute (SCFM) as CFM at sea level with 68 degrees F, at 36% relative humidity.

Note: CFM ratings can be skewed by the manufacturer too. Let me explain

Let’s talk about our third rating, Pounds per Square Inch (PSI). For air compressors the CFM ratings are given at a specific PSI. In other words an air compressor rated at 3 CFM @ 90 PSI should be capable of delivering the 3 CFM at 90 PSI. The problem is air compressor manufacturers can advertise a higher CFM at a specific pressure because the air compressor is capable of delivering the rated CFM going from 0 to 90 PSI, but what is the true CFM delivered at 90 PSI. If your air tools or RV tires require a specific CFM rating at 90 PSI you more than likely won’t get it based on the advertised CFM @ a specific pressure. What this translates too is that it will take a long time to inflate some larger RV tires, if the compressor is in fact capable of inflating the tires at all.

When shopping for a portable air compressor the key is to try and find one that can deliver about 4 REAL CFM based on the REAL HP rating at 90 to 100 PSI.

If you have the storage room available, and you will have access to electricity, you can find some reliable pancake style portable compressors that will do a good job inflating tires and performing other small household jobs.

Happy Camping,

Mark Polk

RV Education 101

RV University

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Mark's RV Tire Tip

Have you ever owned a vehicle and neglected to have the tires rotated and one day you suddenly notice that the front tires are wore out but the rear tires look fine? I'm sure that this has happened to most of us until we learned the valuable and expensive lesson of not rotating our tires. If one tire shows signs of wear faster than another tire it may be a signal that something other than normal tire wear is happening and you should have it checked. But if it's just normal tire wear you can even out the wear and extend the life of your tires by having the tires rotated on a regular basis. Talk to your tire dealer about proper tire rotation intervals.


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Copyright 2008 by Mark J. Polk, owner of RV Education 101

RV Expert Mark Polk, seen on TV, is the producer & host of America's most highly regarded series of DVD's, videos, books, and e-books. http://www.rveducation101.com/

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