Are there stupid questions about tires?

Recently ran across a thread where there was a rather basic question on inflation where someone claimed to have "searched everywhere" to find how much pressure to put in his tires.

After dozens of posts on this blog, I have to admit I am disappointed that he hadn't found any of my info. I do know that many times a simple Google search on the tire-related topic will show this blog a few times.
There are no stupid questions. Ask questions and learn something new every day. But clearly, stupid answers are a real possibility.

I sort of agree but do wish that more people learned how to use the "search" function on forums as many questions have already been answered more than once. Also, learn how to efficiently use Google.

My problem is that I simply do not have the time to answer the same question multiple times a week.

For example "How much air do I need in my tires?"

When it comes to Motorhome tires and inflation it doesn't make any difference if your MH is blue of silver. The way to learn how much air the tires need is the same.  Without making a minimal effort to learn what to do and simply expecting someone to give you the proper answer i.e. "You need to inflate your tires to 94.565 psi" is not the correct answer.

The saying about teaching someone how to fish rather than just giving them the fish applies here.

How do we "teach" people that they need to learn how to search the Internet as the answer to most questions is already there?

 I am pretty confident that with over 400 posts I have at least touched on just about any question people might have relating to Tires or valves in RV application.

 If I have missed a topic please feel free to send me an email (address is shown under my picture on the right).

I do hope we all have a Happy and tire problem-free Holiday.

##RVT927

Why are tires such a hot topic on RV Forums? - Quick question; Quick answer

Here is part of a post I just read...
" I do not understand why there is such an issue on this forum on tires? Yes many RVs come with junk tires and you need to replace them with a better tire as I did.
A few people post the facts but as the saying goes you can lead a horse to water, but you can't make it take a drink."

My reply:
I think the reason tires are a hot topic on each of the RV forums I try and monitor is that most people only have their experience with their personal car as a background. With their car they basically have learned, incorrectly, that they can usually get away with doing zero maintenance i.e. checking load or inflation, and they still never seem to have tire problems.

The reality is that car companies have teams of engineers working on just tires & wheels. The tires have dozens of performance requirements that the tire company must meet before they can sell tires to the car company. In the RV world I think the only requirement from the RV assembler is low cost.

Another thing is that cars specify inflation that gives 15% to 25% safety margin for load (with a few notable exceptions such as Ford Explorer of the 90's with what I think was a 1 psi margin.) This means people can go from oil change to oil change and not have to check their tires and just trusting the service station will adjust the air every few months.

When someone purchases their first RV there is lots to learn and tires are low on their list since they never had problems before so since everyone knows tires are just round black things that cost too much why bother to learn how to make them last?

Then they have a failure or see someone with an RV have a failure and suddenly they learn they need to pay attention. What they get is "Campfire Experts" providing partially correct to completely wrong information.

Then they discover RV forums. So they ask the same questions and with a few notable exceptions they get the same answers they got around the campfire.

I know of only two actual tire engineers lurking on various RV forums. There are few others with what appears to be solid engineering background and sadly a lot of self proclaimed "Experts" who base their answers on their personal experience rather than the Science of tire mechanics.





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RV Travel Webinar Q&A Part 1

I enjoyed this first webinar on the RV Travel YouTube channel (June 28).

Hope you found the information informative.
 The answers had to be short or I am afraid I would have put some to sleep. I do want to provide as
much info as possible so I am reviewing the comments and will provide a bit more information based on the comments






Buddy Light said "I like RV tires with more plies".
    Well Buddy you may not realize but "Ply Rating" is an old term that is based on an "equivalent strength" and not on the actual number of Ply or layers of reinforcement. You can read the material list of what is actually in your tires as it is molded on the tire sidewalls. It may say something like "Sidewall 2 Ply Polyester, Tread 2 ply Polyester + 2 ply Steel".  If you have a large RV with 22.5 wheel diameter you may be surprised to learn the sidewall of many of these tires has only one Ply of Steel in the sidewall with an additional 3 or 4 Ply of Steel in the Tread area. These tires may have a "Ply Rating" of 12 or 14 but in reality there is only 1 ply in the tire.

Astrid Bierworth said "if a truck tire is the same size as the trailer tire, could we get better service from a truck tire?"
    When I heard and answered the question I was not thinking about "Light Truck" tires as when someone says "Truck Tires" to me I immediately think of Heavy Truck tires that have wheels of 19.5" or larger. Reading your question now I think you meant to ask about using Light Truck or LT type
tires on a trailer and replace the ST or Special Trailer tires that came on the trailer originally. On my blog I started a multi-part post 6/23 "Can I change from ST to LT tires on my Trailer or 5ver?" that
addresses your question specifically. The second part will be published next week. If you subscribe to my blog you will get a notice when a new post goes up.

David Lee asked a similar question. "What's the advantage/disadvantage of using light truck tires over trailer tires?"
     Sorry David our set-up didn't allow me to see the comments live. I hope you find the answer you were looking for in my series on this topic.

AaronzDad "Roger are there any tire treatments that will add back the oils and chemicals tires need to stay flexible and extend the life of the tire?"
     No the treatments mostly remain on the surface much like Sun Tan Lotion does when you spread it on your arm. They may give the tire a "New Shine" look and may provide a little UV or Ozone protection but too often many of the treatments and their application can end up doing more damage than good. Sometimes there is "Petroleum Distillate" in the treatment and this can actually attack the tire rubber. Other times the application of the treatment removes the chemicals originally put in the
tire for protection. I suggest you limit your tire "treatment" to the same wash, sponge and soap you use on the painted surfaces of your RV or car.

Lori Singels said "The highly recommended TPMS system I bought constantly leaked. They're now a paperweight on my desk."
      I don't know who gave you the recommendation but if you bought your TPMS from a reputable dealer there should have been a warranty available that would have addressed your problem. I did a post on "What is the BEST TPMS" and in it I tried to provide the features I felt were the most important to look for in a system. Remember that just having a big advertising budget so your product name is most recognized does not mean your product is the best on the market. After some research, I bought my TPMS from TireTraker and have run them on my coach since 2012 and am very pleased.

Request to all posting questions on tires

Just a quick post for those asking questions about tires. Before you post your question on inflation / size/ speed / load etc on any of the RV forums or on this or other tire related Blogs,

Please provide the complete and accurate tire information.
This can be found on the tire placard. Better yet, if you can get it in focus, post a picture of the placard. The tire engineers that follow these posts seem to have to ask follow up questions most of the time as the information provided is not always sufficiently detailed or accurate for us to do more than take a guess.
Some examples of incomplete information include statements such as "I follow the manufacturer’s recommendation"  Which mfg? The tire or the RV?
It is the RV mfg that has the legal responsibility to provide the minimum inflation recommendation for the tires applied to the RV. The inflation level must be sufficient to carry the load as specified on the placard. The tire manufacturer does not know what the RV weighs or what the axle rating is.

Sometimes we hear  "I had my RV weighed and got the inflation"  Did you get the actual corner loads for each position or did you get the total for each axle and divide by two or did you get the total scale weight of the RV and divide by the number of tires on the ground?
Where did you get the inflation information? From your tire companies load/inflation tables or from some self appointed "expert" who invented their own formula (as has been done by some on the Internet) or by asking the guy parked next to you in the campground?

Missing or incomplete information
While we don't need the details on the make & model of your RV we do need to know if it is a motorized unit or a two or three axle 5th wheel or a simple single axle TT. If you want to help others you can include make & model but it takes a lot of extra time to try and research what the configuration is if the tire engineer is not personally familiar with your model. The inflation recommendations for motorized units can be different than for towables. The number of axles is important as it affects the side loading. Also if the tire in question is in a dual position application will affect our answer. While most ST and LT tires have polyester body ply and most 22.5" size have a steel body ply it again will eliminate guessing if you provide the information molded on the sidewall that tells both the number and materials used in the construction of your tires.

DOT number  Providing the complete DOT number can provide valuable information. We can translate the code to know who, where and when the tire was manufactured. With this extra information we might save us all time by suggesting the tires be dismounted and inspected or simply replaced. We might be able to check to see if there had been a recall or other complaints filed with the National Highway Traffic Safety Administration on your brand and size tire. If you are unsure what we need you can always post a clear, in-focus picture of the DOT.

Thanks in advance for your assistance.
We want to provide clear and correct answers to your questions but we do need your help so that we have the information we need to make an informed answer.

How to get your tire questions answered correctly

I have offered to answer specific tire questions on this Blog. I respond to questions on four different RV web sites that have forums where tires seem to be a hot topic. One things is a constant with many who ask questions is that they seldom provide enough information with their question such that I am not forced to ask for more information or guess.
I and the other tire experts on the web have a request.


When asking about specific loads, inflation, alternate size, or specific tire problems it would really help if basic information was provided.

While I and the others are more than willing to consult the standards books or provide an opinion we really can't spend hours trying to first solve the problem of knowing what tire we are being asked about. One thread I am following has over 275 posts but at least 25 - 40% are replies that show the need for more accurate information is needed from the poster.

Please provide the "Complete" size. That would include the Service Description part that comes after the rim diameter as well as the type tire which is the letters up front if any.

235-15 isn't correct but many times that is what we get.
Technically an LT235/75R15 107/110Q Load Range D
is a different tire than a LT235/75R15 Load Range D.

Also concerning the load on the tires. As a minimum you should have a real scale measurement of the total load on all the tires. While you may feel you know a lot about your "Death Valley Special" RV not all of us know if it has one, two or three axles.
Ideally you should have at least once had your RV weighed with certified scales where you can get the individual loads on each tire.
Almost ALL trailers are out of balance axle to axle in addition to side to side with a good portion (usually the ones with tire problems) discovering that they are at least 5% off and sometimes as much as 15% out of balance.
So in addition to the complete tire size how about:
"I guess the 4 tires on my trailer carry 10,000 pounds"
or
"The tires on my front axle carry 5500 and the rear axle 4500"
or best of all
"RF 3300 LF 2200 LR 2700 RR 1800"

Motorized RVs are a little better but still have some out of balance.

Finally if you really want to do a First Class job then the tire brand and design as molded on the tire, the max load at what inflation as molded on the tire and picture -in focus please- of the placard would be of great help.

I know that if given the choice of who to answer first I would answer the person that supplies the most information first.

OK I am stepping down off my soap box now.

Class-A TBR type tires

Previously we talked about the full tire size nomenclature for Passenger and Light Truck applications.

Large RVs usually run what are known as Truck or Bus type tires. With most new applications being of Radial construction we use the acronym TBR. Here are some examples:
255/70R22.5 LR-G 138/134 M
In this example, the various numbers and letters are similar to those for Light Truck except the Load Index numbers and Speed Symbol are optional so may not be marked on the tire sidewall as part of the complete size nomenclature. The Load Index 138/134 and the Speed Symbol "M" make up the Service Description. If this is on your tire please include it when asking a question.

11R22.5 LR-H
This is an old “Inch” size description with the tire being about 11” wide. This would be a tubeless type tire.

10.00R20 LR-H 146/142 L
This is an old “Inch” size description with the tire being about 10” wide. This would be a tube type tire. Again the Load Index and Speed Symbol are optional

8R19.5 LR-F 124/122 L
This is another old “Inch” size description with the tire being about 8” wide. This would be a tubeless type tire with the example showing the optional Load Index numbers and Speed Symbol.
The two Load index numbers signify that the tire is rated for a higher load in single application and a lower rating when in a dual fitment.

The Speed Symbol for TBR tires are associated with the following MAXIMUM operation speeds.
F = 50 MPH G = 55 MPH J = 62 MPG K = 68 MPH and L = 75 MPH
If no Speed Symbol is marked on your tire you need to consider the tire is rated for a MAXIMUM of 65 unless you can find printed documentation from your tire manufacturer stating some higher speed limit is acceptable.
If you are writing to ask a question about your tires please include the complete nomenclature including Load Index, and Speed Symbol if marked on the tire.

SPECIAL SAFETY NOTE: Maximum Inflation
In July, MOTORHOME magazine published an article on TBR tires. The author offered his personal opinion that it was acceptable to set inflation higher than the Max marked on the sidewall of a truck tire. Exceeding the max cold inflation on the sidewall has serious potential safety consequences. Large TBR tires have been known to explode and personal injuries and even deaths have occurred when proper inflation procedures are not followed. I can find no industry guidelines that allow this procedure of exceeding the maximum inflation when setting the pressure for normal highway application of any tire.

Rims also have a Maximum rating for both Load & Inflation.
Many wheels have these ratings marked on the rim. If you can’t find that information I strongly suggest you contact the manufacturer and obtain the ratings for your rims. Again Serious injury or even death can occur if a rim fails due to damage and overinflating or improper assembly.
Accuride Safety information and Product Literature you can consult.

Alcoa also has product literature online.



Inflation Safety
Whenever we are talking about setting the inflation in a tire, we are talking about “cold” inflation. This means the tire is at ambient temperature and not warmed from operation or sitting in the sun.
I would suggest the tire not be driven more than two miles in the last hour and not in direct sunlight for at least two hours. When I did my tire cover study – See my post from June 16 on Tire Covers, I saw almost 40° increase in tire temperature in about one hour for a tire in full sunlight.

I would strongly suggest you never attempt to inflate a TBR tire if the tire beads are no longer fully seated against the rim without using an approved Safety Cage. If there is a problem, the tire and wheel can separate and components can easily go through concrete block wall never mind the side of an RV.

Any tire that has lost more than 20% of its rated inflation is considered flat and if it was driven on in a “flat” condition it needs to be dismounted and inspected by trained tire company store technitians. Not a Mom & Pop garage but a store run by a tire manufacturer.

Do you have questions?

I can only guess at what your questions might be about. If you want to know something about tires post it as a comment here and I will make a list of topics to cover.
No guarantee, but if you don't ask, I may not think of the topic you want to know about.