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Sunday, April 17, 2016

How to Maximize tire life with minimum effort

If you are new to the RV lifestyle or an old hand with many thousand campfires under your belt, there is one thing that is true: What you knew or learned about tires from years of car ownership probably did not prepare you for the task of maintaining the tires on your RV. This is true if your RV is a 18’ Travel Trailer or a 45’ Diesel Pusher.
I think we all understand the concept that a system is no stronger than its weakest link. For many RVs, the weakest link that can interrupt long term, problem free travel are the tires. Car tires have evolved with improved durability and reliability to the point that many people may never need to touch their tires or even know how to change a tire. Today, some cars don’t even have a spare tire and if they do the driver may not have even bothered to learn where it is as the expectation of needing to use the spare is so low it has completely dropped off the radar screen.
As a retired Tire Engineer with 40 years experience in design, evaluation and quality assurance of tires I would like to offer some suggestions that I believe if followed, will lead to many years of problem free travel. I also believe that once you take the initial steps I outline, you will also find that you will only need to spend about 15 minutes a month, or less on average with tire maintenance.
The basics that are needed to have a tire problem free experience with your RV tires involve two simple steps:
1. Knowing the proper level of tire inflation on your personal RV and
2. Ensuring your tires are always inflated to that level.
There it is, just two simple and rather basic steps and, you don’t need to be experienced in vehicle mechanics or tire engineering to accomplish these two steps as I am going to share the steps that have worked for me and thousands of others for decades.
Step 1: Knowing Your Proper Inflation
So the first step is to know the proper level of tire inflation on your personal RV. The important concept here is “Your RV. Not the RV your brother-in law uses, or the inflation the guy in the campsite next to you uses, or even the level provided by the RV manufacturer on the tire certification label, otherwise know as the “Tire Placard”. Now some will point out that the RV manufacturer has the responsibility to inform you of the minimum tire inflation you should use, and this is correct, but this is based on an assumption which may mean the numbers are too high or too low for your RV when you have it packed with the stuff you want to take along on your next trip.
This step takes the most effort, but you really only need to do it once over the years you own your RV – unless you make a major change such as add a generator or refinish the interior with granite counter tops; you know, do something that significantly changes the weight of the RV.
To learn your real weight you need to pack your RV with all the clothes, food, fuel, water and other “stuff” you expect to carry, including the proverbial "bowling ball collection." Once it is fully loaded, you and the family need to take a short trip to a local feed store or gravel pit or truck stop that has a large truck scale with enough side clearance that will allow you to get the tires from just one side of the RV on the scale. Obviously you will need to do a bit of preparation to find such a scale, so some time on the Internet or with a phone book is in order. It is suggested that you review the worksheet before heading off to the scale so you get all the facts you need in one trip.
Here is a company that travels the US and specializes in properly weighing RVs and giving the owner the load numbers for their personal unit.  " RV Safety & Education Foundation (RVSEF) This leader in safety education in the RV community offers wheel by wheel RV weighing services for all types of RVs.
If you will not be in one of the locations where RVSEF is offering their services then you will need to do a little research, as not all truck scales have the side clearance needed. You should know that some truck scale operators discourage side to side weights and have installed guard rail to prevent this. When you check out the work sheet you will have a better understanding of what is needed.
Our friends at Fifthwheel St have a web site has information including a video that focuses on trailers but has video showing the process which is similar for motorhomes.
Bridgestone has a page just on RV tires with a worksheet for calculating tire loads
Goodyear has a nice site too
Here is the Michelin RV tire page
If you look at more than one of the above links I think you will see that everyone offers the same basic information on the process. You do not need to worry about which worksheet you use as the math is the same for everyone.
After you complete your worksheet you should know the actual load on each tire position. The next step is much easier and also only needs to be done once. You need to confirm the minimum cold inflation your tires need to carry the load. It is always a good idea to use the tables published by your brand tire. Here is my blog page with links to many different brand tires. Simply go to your brand, find the table that has your size tire and look for the inflation that supports your load or more. Don't worry if your brand doesn't offer tables as almost all companies follow the same published industry standards.
Also don’t be tempted to go to a lower level of inflation if your numbers are close. Always go up.
Now you know the minimum Cold Inflation Pressure or CIP.  Wait! What do I mean by CIP? Whenever tire inflation pressure is measured or set the tire needs to be cool and at the same temperature of the air and in the shade. This means not having been driven on or in direct sunlight for at least 2 to 3 hours. Tires get warm when moving and the Sun heats them up which results in a higher temperature which results in artificial increase in pressure. Many people simply do their tire pressure check in the morning before starting out or late evening after a day of travel. Either way the tire needs to be cool and in the shade when you check your pressure.

I feel the CIP needs to above the minimum needed to carry the load as if there is a drop in temperature you may end up below the minimum if you cut things too close. I suggest you run +10% above the Minimum for your personal CIP.
A couple of details and a suggestion:
All tires on each axle should have the same inflation. This means that whatever inflation numbers you have for your tires select the highest from the tires on any one axle and use that number for all tires on that axle. This will give you more uniform stopping and steering response.
Over the past few years technology has evolved that allows you to monitor your tire inflation as you drive down the road and can warn you if you pick up a nail or other damage. You have this in your car and it is that little orange symbol with the exclamation point in it.
and now you can add this safety feature to your RV trailer or motorhome. It is called a Tire Pressure Monitor System or TPMS for short. A quick internet search will identify a number of units specifically designed for RV application or you can review THIS web site for a discussion of features to consider when shopping for a TPMS.
A bit of Truth in Advertising here. This blog is currently sponsored by Tire Traker brand TPMS. As you might expect that is the brand I have run for years. What you may not know is that I bought my TPMS from Traker before I started writing this blog.
One nice feature of having such a system is you do not need to get out with your digital pressure gauge and check your tires every day of travel as the TPMS will let you know your inflation in the morning while you stay inside with your coffee and more importantly while going down the road. You will quickly learn the details of your pressure reading in just a few days of observation.
So there you have it. Get the RV weighed when fully loaded and do the calculations using the worksheet to learn the actual tire loading and the inflation your tires need.
Step 2: Ensuring That Inflation Is Properly Maintained
This step is much more straightforward. Just check your tire pressure every travel day, or better yet get and use a TPMS (Tire Pressure Monitoring System) to constantly monitor your tire pressure. I even set my low pressure alarm level so I would get a warning before the pressure drops below the minimum inflation I need to support the measured load on my RV.
I believe that if you follow this advice you should reduce what otherwise might be a less than 5% chance of having a tire failure to less than ½% chance of tire failure.

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  1. Great info, thanks. I have a truck camper on a 1 ton dually GMC truck. Given my axle weights, Michelin tables indicate really low minimum CIP for the rears (35 psi), whereas I've been running 65 psi per the placard. Should I really consider running at about 40 psi? Kinda scary. Thanks!

  2. 35 sounds very low. Are you sure you are reading the Michelin tables correctly?
    I assume you have a 10,000 GAWR rear axle so if you have LT235/85R16 LR-E tires with 2,500# per tire your minimum inflation should be at least 70 psi and that is assuming perfect side to side loading. What is your actual rear axle load with the camper and truck fully loaded?

    1. Sorry for the late reply - I had unexpected shoulder surgery 5/3!
      The rear axle GAWR is 9375 lbs. Tires are LT235/80R17E. Fully loaded rear axle load (CAT scale) is 3500 lbs (both sides).
      Thanks for all you do!

  3. I contacted the maker of my tire and they pointed me to the maker of the RV. So what do I do if the load inflation table does not have the weights for my tire size included on their table. My tire size is there but my load is not. The first closest number is 800lbs higher...

    1. If you go off the Load Inflation chart on the bottom end simply use the lowest inflation shown.


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