TPMS don't prevent Blowouts

A reader wrote
"I'm a firm believer in a TPMS, but with that being said, I have a digital gauge. I set my pressure from that and then read from the TPMS I have installed. That has given me the plus or minus of the system which they claim can be plus or minus 1 or 2 PSI. Blowouts seem to happen no matter what precautions you take. I have been to the scales I know that I'm not overweight, I know that I have even wear. I know what my cold PSI is. So what then is a person to do more than that? I do not have control over the manufacture process, so you trust the dealer and data that they supply. So why are trailer tires so much more susceptible to blowouts than tow vehicle tires? A TPMS system cannot predict a sidewall blowout. To me that has to be the cord or construction of the tire itself. It will give me a pressure loss and then you still have to slow and pull off in a safe area that's where the damage occurs. So what are we to do or what do you recommend about that scenario. Thanks for all your help."


By "blowout" I will assume you are talking about "run low flex failure" of the sidewall and not the completely different "belt separation". As such if you can avoid driving at highway speed after the tire has lost significant inflation you can avoid having a run low flex failure, i.e., blowout. So it follows that if you stop driving on a tire after it has lost 30 to 50% of inflation or more, then you will avoid having a sidewall blowout.

I know of no part of the tire manufacturing process that can somehow manage to place "defective" material in a consistent circumferential line only in the upper mid sidewall. Also to my knowledge, no one has been able to identify exactly what the "defect" is that is located at the site of the melting.
Melting of polyester cord can occur no matter the size or number of cords if the sidewall is overstressed (bent) at a high rate. It does, however, take probably about 10 to 20 minutes for the temperature to rise to this level. This type of failure will and has occurred in all brands, so again, what is the exact defect.

In steel body tires we see the same circumferential line with signs of fatigue failure of the steel cords when they are run when significantly underinflated.

The reason trailers have a higher rate of sidewall flex failures than tow vehicles or motorhomes is twofold. First, a tire losing air on a tow vehicle provides the driver the opportunity to feel the change in ride and handling but provides no such tactical feedback if on a trailer. Second is the internal structural stresses that trailer suspension design place on its tires that are not experienced in as high a level in tow vehicle or motorhome applications. Interply shear is about 24% higher in trailer application than in a motorized vehicle.

I suggest you check the Label list on the left side of this blog and review the posts that have a label "Blowout" if you want to learn more.

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Tire sidewall "strength". What does that mean?

I note that on many RV forum posts on the topic of tire "Blowouts," there many times are posts on the "Strength" of the tire sidewall. Before I start, it's important that we have a shared definition of a few words.
"Blowout" is simply a statement that a tire failed catastrophically. It does not mean it simply exploded as if it were a bomb.

Belt or Tread Separation is the detachment of the belts and or tread in a radial tire. This can lead to a rapid loss of air which can make a loud noise, surprising the driver and leading to the idea that there was an explosion or "Blowout". But not all tires that have belt separations end up with a rapid loss of air. Here is an example of a tire with tread & top belt detached from the rest of the tire. It is shiny as I sprayed water on the tire while inflated on a wheel to inspect for punctures or leaks as I had suspected the tire had been run with low inflation. I "redacted" identifying marks as that information is not important for this discussion.

Sidewall Failure for this discussion means a failure of the tire sidewall not related to a sidewall cut or impact. many times when a tire loses air but is still being driven at highway speeds, the body cord or "body ply" material can fail due to excessive heat.  A more technically accurate term used by tire engineers would be "RLOF" which stands for Run Low Sidewall Flex Failure. Most Passenger, Light Truck and ST type tires made today use Polyester cords the sidewall ply.  With excessive flexing and bending from low inflation, the cord can overheat.

If the temperature gets high enough (300°F to 350°F) the cord can lose half its strength and high temperatures can result in the cord melting just as you have seen when you melt the end of a piece of Nylon or Polyester rope with a match.
 Here is what melted tire cord looks like.

I have shown this condition in a few posts, but probably the one with the best example is my post "Blowout- Real Life Example"

So why does this engineering stuff make a difference? You still had a "Blowout," and are not happy. Probably want to blame someone and the tire company is an easy target. BUT as I have said before if you do not know the real reason for a tire failure you might not prevent another failure from happening.

Imagine you had an RLOF but did not bother to try and learn why the tire was low on air. Puncture, cut, leaking valve, leaking valve core, cracked wheel are all "suspects" and just replacing the tires on your RV with a different brand will not prevent another "Blowout".

So this leaves the question of Sidewall Strength. DOT has a specific test to confirm a minimum "strength" for tires. The test procedure. involves forcing a 3⁄4 inch diameter steel rod with a hemispherical end perpendicularly into the tread as near to the centerline as possible,  at the rate of  2 inches per minute. This is repeated 5 locations around the tire and there are published minimum energy requirements (inch-pounds force) that tires must exhibit. These minimums are based on the tire size, type, and Load Range.

Now you may ask: How does the sidewall material strength come into play? Well, the sidewall material runs under the belt material so is part of the total strength requirement. Tire companies also have their own "Burst" test requirements which involve mounting a tire on a special test wheel and increasing the pressure till the tread or sidewall or the bead fails. They use special wheels as most tires are stronger than regular production wheels. The minimum pressure is not published but in most cases, it is in excess of three times the inflation number molded on a tire sidewall. and in some cases, I have seen tires exceed six times the inflation number on the sidewall.

Tire Design engineers have a wide choice of sidewall ply material to choose from. Different types of cord, different sizes and even different amounts or cords per inch circumference can be selected as the engineer works toward the final design specification. Simply claiming that "Our tires have larger and stronger cord" while true doesn't address the question of how much of that cord is used in the tire.

Bottom Line. I hope you now understand how simply claiming the tire sidewall wasn't strong enough will not help you solve your tire failure issue.

Travel Trailer tire "Blowout" not quite.

Just got an email from a reader, in which he describes a recent tire failure he experienced on his travel trailer. He reported:

"Mr Marble,
I recently experienced a catastrophic tire blowout. I am 100% confident it was not due to low tire pressure (according to my tpms). My tpms did not alert me to an overheat or pressure issue. I was only 35 miles into my trip. It alerted to the blowout 3-5 seconds after the blowout, but I had already heard the pop and saw tire and fender shrapnel flying in my side view mirror. It was passenger front tire on trailer.
Tires are approx three ears old, around 5000 miles on them. We are weekend warriors plus 1-2 1000 mile trips per year. Rig sits 2-4 months of the year under shed cover with covers on tires on gravel.
Before I go in to details on rig and such, would you be willing to give me your opinion as to the cause of the failure? I have my suspicions but I'd like to hear from an expert.
I put the spare on and finished my trip and am sitting at ocean lakes family campground in Myrtle beach. Can take pics/video and provide whatever data you need.
Here's a couple of pics if it helps sway your decision.
RW-Myrtle Beach"

Here are the pictures he sent of his tire.

  Now many of you might think these are sufficient but for me to provide a better more accurate opinion of that went wrong I really do need better pictures.

In this case it was too late to get better pictures as RW informed me that he didn't have room to save the tire till he got home.

A few comments and observations.

The tire did not suffer a "Run Low Flex Failure" or what is normally called a "Blowout" by a non-tire engineer. The condition of the tire is more accurately a Tread or Belt Separation. The air loss came after the belts and tread had already separated from the body or carcass of the tire so that is why the TPMS did not provide any warning.

I did inform RW that the pictures were not close enough or of high enough quality to allow me to zoom in to see the details needed for me to establish a reason for the failure with a high degree of confidence but I did provide some comments.

A tire suffering a Tread Separation is simply not going to generate high enough temperature to trigger the TPMS.

It appears that this tire possibly suffered from some manufacturing or chemical problem as there are large amounts of steel cord with no rubber adhering to the steel cords. This could be because the tire had started to separate many miles prior to the external failure and the rubber was abraded from the steel cord. I would need to do microscopic examination to confirm this diagnosis.

I suggested that RW review the "Free Spin" tire inspection process that I outlined in my post on How to Inspect tires and in the post Why Blowouts are of special concern.

I also suggested that he include the Free Spin inspection procedure at least once a year so he would improve his chance of discovering an impending tire failure in the future.

A side comment about retaining the tire. If RW had wanted to file a warranty claim with the RV dealer or tire company he would need to be able to produce the tire for examination. It would also have been a good idea to be sure he had recorded the complete DOT serial and file a complaint with NHTSA for without complaints there will never be an investigation or a possibility of a recall or an improvement in the quality of tires produced for the RV market.

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Was your "Blowout" caused by parking at Quartzsite two years ago?

This is a bit of a continuation on the topic of "tire Dressing" from last week's post.

I do wonder how many that complain of sidewall cracking or less than desirable tire durability makes the effort to protect their tires from the heat and UV degradation from direct sun exposure.

While there might be some benefit and shielding from applying such as "Dressing" or "Shine" or other "stuff" to the tire sidewall for UV shielding. No dressing will protect a tire from the accelerated aging process due to being "baked" by the sun's heat.

There is no standard SPF for tire dressings as there is for sun-tan lotion, It would not be that difficult to measure the level of UV shielding by measuring the UV going through some clear plastic sheeting and then applying the tire dressing to the sheeting and measuring the level of reduction if any in UV rays.

In many cases, the rubbing of the tire sidewall when applying a dressing can remove the special anti-oxidants and UV protection provided by the chemicals the tire companies use in all tires.

All rubber, natural or synthetic, loses strength and gets stiff over time. The rate of degradation is also temperature-dependent with the rate effectively doubling with each increase of 18° F. As I have shown in my blog on the use of tire covers sunlight can easily accelerate the rubber degradation by 4 times with 8 times not unreasonable in Southern states. This loss of strength and flexibility can eventually lead to a belt separation, which many sometimes call a "blowout". Maybe that unexplained "blowout" in June was brought about by the eight months of direct sun exposure in Quartzsite, AZ, over the last two winters.

I have confirmed, with temperature measurements, the significant temperature drop with the use of white vinyl covers on Class-B, Class-C and RV Trailer sizes, and the use of a flat mesh "Tire Shades" on Class-A motorhomes. I would recommend against the use of black or dark color solid vinyl covers as they would act more like an oven by both transferring the sun's heat to the tire and preventing cooling air circulation around the tire.

##RVT948

Tire Blowout - China-Bomb or Pothole?

Hardly a week goes by without someone posting that they had a "Blowout" and since they had checked the tire air that morning, they "knew" the blowout must have been caused by a defective tire. Many times they jump to the conclusion that because the tire was not made in the USA, that fact seems sufficient in their minds to establish certainty.

I have posted replies that just because they had checked their tire a few hours prior to the failure, that is not sufficient proof that the failure was due to a defective tire. In my experience the vast majority of so-called "Blowouts" are actually "Run-Low-Flex" failures. A tire can loose air for any number of reasons such as puncture or valve leak or even an impact.

I am a strong advocate of TPMS as they can warn of air loss but even the best TPMS cannot provide warning of a catastrophic air loss that can occur after impact damage.

Those that have attended one of my seminars may remember my story of the two impact failures my then fiancee had and how both tire failures occurred some 20 miles after the actual impact. I am sad to report that I suffered an impact on my personal car. I do not remember hitting a specifically large or deep pot-hole with the LF tire but luckily for me I noticed a bulge on the outer shoulder of that tire.

When I saw the bulge I knew at once I had a failed tire and it was only a matter of a few miles before there would be a sudden rupture of the sidewall and the air would rush out the 1" plus hole. Too fast for my TPMS to provide a warning. I recognized the signs of an impact because I have inspected hundreds of tires with similar damage. Some were hard to find as the damage was not even visible after dismounting the tire while others had "blown" while the vehicle was parked so there was no damage from running on a tire with zero psi.

The silver lining to this is that it gives me an opportunity to show the results of my step by step examination. Hopefully this will allow you to have a better understanding of how proper failed tire inspection is done and note that simply jumping to conclusion that since the tire was not made in the USA the country of origin played no part in causing the failure.

Here is the dismounted tire.

 Note the signs of damage are essentially invisible BUT since I did a complete examination before dismounting the tire I can show the physical evidence on the rim that shows the marks left by the tire as it was severely deflected and bent down over the rim even though fully inflated.

  The small lines were left from the sidewall decoration on the tire where it contacted the rim.

Here you can see the break in the interior where the body cord failed under the shock load.

Before I dissected the tire I continued my visual inspection and noted marks on the interior opposite the fracture. You can see where the tire was bent and over extended but did not fail.

A close-up showing the failed body cord. This "crack" measures about 0.6" long

.





Here is a video.

Watch the rubber to the left of the break. See how it stretches in a strange manner. The body cord under this rubber is also broken but not visible as the interior rubber has not failed yet. Sometimes all I find are signs of this stretching that indicates hidden failed body cord.

Hope this helps some understand what can happen. If I hadn't happened to see the bulge I definitely would have suffered a rapid air loss with possible vehicle damage or even loss of control and worse.

I read it on the Internet

With apologies to the "French Model" guy in the TV advertisement, I want to talk about the reliability of tire related information as seen in many RV forums.

 I subscribe to or monitor about 10 different RV forums. I know there are more but I do have other things to do than just read RV forum posts.

 Many times I use the "search" function to look for threads that are about tires. It appears to me that a significant percentage of the people asking questions, have not made an effort to seek out answers already posted before they ask a question. Too often what follows are answers from other RV owners who clearly do not have a good engineering background on the topic of tires. I would like to post a few examples and point out the problems I see in both the question and answers provided by others. 

An owner said “I have a 1992 Ford Four Winds motor home. 29 feet, I think. What kind of air pressure would I run in the tires. I have 60-70 but have read where some run around 100. Please help me decide".

Well first off the poster of the question left of much important information out of his post. What was his current tire size or the original tire size, including Load Range and what are the actual loads on the individual tires.

Clearly he had not noticed in numerous other threads that there is no “rule of thumb” for providing the proper inflation other than following the vehicle tire placard information. I would not be surprised to learn that this owner doesn’t even know he has a certification sticker.

What followed were 4 posts telling him the proper inflation for a motorhome, is a function of the real load and there are too many variables such as model, kind & size of tires to provide an answer. Another person replied that he should read other posts about tires and review the tire mfg “Load Charts”. Another asked for the tire loading but also mentioned the need to know the tire age by reading the DOT serial. Finally a more knowledgeable person suggested the tires need to be checked for sidewall cracking and pointed out the tire “birth date” is part of the DOT serial.

As of a week later the OP has not replied with any of the requested information. I think you can see that if he had made a little effort and read a few posts, or my blog :-) he would have been able to learn the answer to his question right off.

In another forum a person posted complaint about “blowout”.  Here we see the picture he posted.

 In this close-up you can see the tread on the right side is much more worn than on the left side.

 This is evidence of the detachment being in the tire for many hundreds of miles.

This thread has over 20 posts with lots of complaints about junk tires etc but not one properly identified that the subject tire did not have a blowout as it still held air. At that point I jumped in and provided a number of pictures of other tires showing the wear was not due to brake lock-up and the tire did not have a “blowout” but had a belt detachment and that if the tire had been more thoroughly inspected the failure and RV damage could have been avoided.

I suggested that if you have an RV, especially a multi axle trailer, an in the air rotation to look for tread wobble is something I would suggest at least once a year starting at year three.

This video  shows what a bad tire can look like.

Bottom Line.

If you have a question First spend a little time and see if the question has already been asked. Second, was the answer based on a lot of complaining and ranting or was the answer based on facts with pictures, links and hard data.

Remember that just because you read it on the Internet doesn't mean the information is correct.

“I had a Blowout”

That’s an all too often statement heard from RV owners.

According to some data a significant portion of RV owners have experienced a tire failure in the past two years. All too often the tire is blamed but my experience from examining thousands of “tire failures” is that the vast majority of these failures can be traced to the service conditions and not some so-called defective tire. Let’s look at a few examples.

Here we see an LT type tire that is now in two pieces







This picture shows the classical “Three piece Flex Failure”. I bet you see a tread ring like this almost every day in your travels.




This tire was one I did an “autopsy” on. Looking at the “broken edge of the sidewall we can see hard body ply cord.





Taking a microscopic look at just one end we easily see the fused cord.








This is much like what we have all seen when we cut Nylon or Poly rope and then melt the end with a match. Click on the picture for a better view.
It takes excessive flexing at a high rate to generate sufficient heat to melt the cord like this.
This Body Ply cord melts at approximately 495°F. I usually say the tire was operated at less than 20% of the proper inflation and at normal highway speeds to generate this level of heat.

Before you say “Ya but I have steel body ply so it’ can’t melt”, just think about how easy it is to break a paper-clip by flexing it back and forth.




Here you are looking through the hole in the sidewall of a 22.5 size tire that ran low at highway speeds but lost it’s air because of a bad valve leak.


So was this “blowout” the fault of the tire? Or was there some reason the tire lost most of its air pressure which let the tire flex excessively? I say that based on a majority of tires I have examined, "Blowouts" like these are really Sidewall Flex failures from being operated at highway speed while the tire has lost 3/4ths of it's inflation



Next time you see a tread ring by the side of the road or hear someone say “I had a blowout” you now know one of the probable causes.

Finally, You might ask if there is a way to prevent a sidewall flex failure. I believe that if you have a properly functioning TPMS it should warn you before the tire has lost 20% of it's air. If still inflated to this level it isn't considered officially "flat" and I have never seen a tire that can generate the heat necessary to fail a sidewall if it hasn't been run "flat". If you can set your TPMS to warn you if you either loose 10% of your air pressure or it sees a temperature over 170°F in most cases you will have sufficient warning to avoid this type of catistrophic failure.

A Tire Autopsy "Root Cause" Part 2

Last time I outlined the difference between reporting a condition such as "The tire went flat" and the Root Cause or fundamental reason why a tire is in the condition it is in. This is a critical item if you want to try and prevent another tire failure. This time I will cover one of the more common conditions many call a "Blowout".

What we are looking at is the evidence and tell-tale signs that point to the fact that the "Blowout" was really a Flex Failure of the sidewall due to a tire running at highway speeds while seriously underinflated. This happens so frequently we have a special name for it "RLOF" short for Run LOw Flex.

Here are a number of examples. While many are passenger tires some are Light Truck.

 

In each case there was melted polyester body ply cord. Polyester melts and fuses just like the nylon rope you get at the hardware store and hold a lighter under the end to melt it to stop it from fraying. Body ply looses about half its strength near 300°F and melts at about 395°F.

  

Sometimes the speed, tire size and load conditions cause the tire to fold and buckle which results in this saw tooth appearance. I have seen a video posted of a failed tire and while the shot is short I think it had this condition.

  Last weekend, I happened upon an RV that had just suffered a tire failure. I stopped to see if they needed help. After we got the tire changed, I noted the evidence of a RLOF. The tell-tale flex zone running 360° around the tire making it look as if someone had cut the entire circumference at the same location on the sidewall.

The above tire looks pretty bad but under close examination  I quickly found the proof (melted cord) of RLOF.

Just so you Class-A folk don't feel left out here is what a RLOF can look like with steel body

 

So here we have a condition RLOF that is much more descriptive than "Blowout. When we say RLOF then you know the Root Cause was the thing that caused the air to leak out. Could be a puncture, leaking valve, lack of maintenance, impact or other external damage so we could continue our examination to see what caused the air to leak and then we have a chance to take corrective action to prevent a recurrence. What I do not see is a RLOF caused by bad tire design.

Finally almost all the above might have been prevented if the RV had a TPMS as the driver should have been warned well in advance of the tire loosing more than 10 to 15% of its air not the 50% to 70% loss that results in a RLOF.

Claims of "defective" tires causing "Blowouts" continue to be posted on YouTube

 Here is a post from, July 22, 2012. The owners of this Airstream continue to use the word "defect" but also fail to identify the defect. I also see no signs of them running a TPMS.

"Blowout" A Real Life Experience

In the previous post, I covered Run Low Flex Failure, RLOF, and how there were telltale signs or physical evidence that while each taken individually are just circumstantial in nature but when taking as a whole make a very strong case for the tire having been operated for a number of miles at very significant air loss. In this post, I want to walk you through the thought process of a forensic analysis of the evidence that is available and show how an opinion or conclusion is reached.

First I need to tell you that I have not had the opportunity to personally inspect the subject tire, but there is a YouTube video and I will show you some shots from the video and tell you what I see in these shots. Second I cannot tell you about the individual as I have had only limited correspondence about this tire failure but according to statements in the video they called it a "Blowout", said they had checked the air pressure in the morning and had only driven about 45 miles before the loss of air occurred.

So lets see what the pictures show. I have highlighted the area of interest in each picture. In pic #112 we see in the yellow area signs that the interior of the tire was worn from abrasion on the inside of the tire under one side of the tread rubbing on the inside of the tire above the wheel. This occurs at 0 psi but takes more than the half mile it takes to come to a stop to wear this much. Also the tire must still be in one piece such that the tread can uniformly contact the lower interior of the tire so the wear occurred before the tread part of this tire broke away. In the red area we can see a few dark holes where the body cord has melted and shrunk back into the tire structure. This occurs when the body cord exceeds 390°F. To put this temp in perspective properly loaded and inflated tires may get to 160°F and ultra high speed tires such as seen at the Indianapolis 500 may see 200° to 210° but rubber starts to come apart an just a little more than that.


In pic 108 is another view of the same location of melted body cord. If the cord had simply failed due to high pressure the cord would be frayed. Also note the nice circumferential line the failure took. More on that later.


 Moving on to picture 057 note the areas circled in red. An alternate view is seen at the arrow in pic 426. Now if we compare the loss of the ridge that is easily seen in pic 121. What this means is that the upper sidewall was in contact with the road surface for a number of miles and the outer edge of the sidewall "Scuff Guard" raised rib has been completely worn down. What we do not see is the lettering of the "Scuff Guard" worn away so we know that the wear was not due to the trailer being repeatedly parked against a curb.


+++++++++++++++++++++++++++++

Now I am sure some are wondering how I can tell the difference between running a tire at 5 psi vs 0 psi. Well here are some shots from an experiment I ran myself a few years ago.


  This first picture here on the left shows the wear of the upper sidewall that occurred in only 3.9 mi while the tire had a minimum of 5 psi cold inflation. This is a bit like the wear on the RV tire sidewall

The next picture is of the interior of the same tire. You can see the nice circumferential crease/crack that has formed. This tire did not generate enough heat to melt the body cord as I was driving at less than 10 mph for the 3.9 mile test. That crease is at the location up the sidewall similar to where we see the circumferential failure in the "Blowout". Note there is no contact between the inside of the tread and the inside of the tire above the wheel as seen in the RV tire.

If you look at some of the examples shown in the previous post you will note that many show the same nice circumferential failure line.

Here are some examples that I use as ref pictures to help me understand the Root Cause of a tire failure.

Here are pictures of melted body cord, broken body cord and the holes sometimes left when the cord heats up and shrinks as it melts.
I hope this helps you see how easy it is to be mistaken when you think the failure is because of a defective tire when in fact the evidence shows the tire lost air, the Rv continued down the road at normal highway speed and after a few miles the tire "blew out". The only way to have some warning and to protect yourself against this all too often type of failure is to have a TPMS which will warn you as soon as the tire loses 10% of its air.


Bottom Line: I do not think this tire was "possibly defective" or a "crap tire". It did not "fall apart for no apparent reason". It came apart because it lost its air and the operator did not know till too late.  

 

##RVT976

TPMS batteries, Changing tires, Tire Size info, ST type tire speed rating and RV control with tire Blowout

Few quick topics in this post.
Saw a few posts on RV forums on TPMS sensor replacement.

It seems some people have had their TPM systems long enough that they need new sensors

because their batteries are low. So some folks are confronted with spending $200 to $300 on a set of 6 sensors.  I suggested that they look into the TireTraker system as it has low cost watch batteries so the cost is only a few bucks for a new battery rather than $35 to $50 each sensor. Full disclosure. TireTraker is a sponsor of this blog but I did buy my TPMS from them at a rally a couple years ago based on their features.
I suggest you do a "Life Cysle" cost comparison based on 5 years. Include the initial system cost, the cost of replacing the batteries if your system allows that or the cost of replacing all the sensors if you can't replace just the batteries. You might also want to consider the length of the initial warranty.

+++++++++

Another person said he had 8 years on his Class-A tires and was asking "What brand should I buy"? 

This of  course immediately started a flurry of "I have had great success with Brand-X" or I had a failure with

Brand-X so will never buy another one of their tires, etc.
I asked the poster why he was considering changing brands if he had had 8 year  good service from the tires he had? When it comes time to consider new tires I suggest you make a list of the Pros and Cons of your current tires.

 Be sure not to include things like the puncture with the roofing nail as that can happen to any brand tire.

 I often tell people you are buying a tire company and their dealer network not just a set of tires. If you get a great price from Billy-Jo-Bobs Cheap Tire Emporium and Bate Shop but there are only a handful of dealers in the country where you can get a replacement and you have to pay shipping back to Billy-Jo if you want to make a warranty claim I doubt that the total price of owning that set of tires is as good of a deal as you first thought.

++++++++

When asking a question on an RV forum, it helps if you include the complete tire size designation. Some folks say nothing about the size but want specific answers on load capacity. Others provide only part of the size such as 235/75R16 and leave off if they are talking about a "P" type or "LT" type or "ST" type. The answer to these questions will probably depend on which type of tire we are talking about. It also helps if you include the Load Range as in LR-D or LR-F or whatever is molded on the tire sidewall.
Sorry but indicating that you have a Mountain Top Rambler RV doesn't help as there are just too many makes and models of RV out there for anyone to know all the tire options that migh be used.

+++++++
ST type tires have a normal Max Speed of 65 mph. You should consider this like the redline on your engine. While it is possible to exceed the red-line it isn't good for long term durability. When covering this topic some point to the Goodyear Tech Bulliten that indicates you may increase this max speed rating up to 75 mph if you also increase the tire inflation 10psi above the inflation associated with the max load on the tire sidewall. While Goodyear may be willing to stand behind the warranty of their Marathon ST type tires at this higher speed you should not do the same for other brands of tires unless you get something in writing from that tire MFG. Tire company Tech Bullitens only apply to the brand and line of tires mentioned in the bulliten.

++++++
Finally I had a question on what to do if you have a  blowout on your RV.  Michelin has a good video on this topic covering Motorhomes. Similar driver reaction if you are driving a tow vehicle would probably apply, so there isn't much I can add. The question however asked about blowout on an RV trailer. Now I have not tested this myself but I have seen more than one example where the impact on vehicle control was so small the driver never knew he had a trailer tire failure till someone flagged the driver down.
As explained in the Michelin video the forces would be drag on the trailer which would keep it generally straight behind the tow vehicle with only a little side offset.
If your trailer did start to sway I would use the manual brake control to slow the trailer down. This should quickly stop the side to side sway and allow you to bring the tow vehicle and trailer to a safe stop.

"Blowout" A Real Life Experience

In the previous post, I covered Run Low Flex Failure, RLOF, and how there were telltale signs or physical evidence that while each taken individually are just circumstantial in nature but when taking as a whole make a very strong case for the tire having been operated for a number of miles at very significant air loss. In this post, I want to walk you through the thought process of a forensic analysis of the evidence that is available and show how an opinion or conclusion is reached.

First I need to tell you that I have not had the opportunity to personally inspect the subject tire, but there is a YouTube video and I will show you some shots from the video and tell you what I see in these shots. Second I cannot tell you about the individual as I have had only limited correspondence about this tire failure but according to statements in the video they called it a "Blowout", said they had checked the air pressure in the morning and had only driven about 45 miles before the loss of air occurred.

So lets see what the pictures show. I have highlighted the area of interest in each picture. In pic #112 we see in the yellow area signs that the interior of the tire was worn from abrasion on the inside of the tire under one side of the tread rubbing on the inside of the tire above the wheel. This occurs at 0 psi but takes more than the half mile it takes to come to a stop to wear this much. Also the tire must still be in one piece such that the tread can uniformly contact the lower interior of the tire so the wear occurred before the tread part of this tire broke away. In the red area we can see a few dark holes where the body cord has melted and shrunk back into the tire structure. This occurs when the body cord exceeds 390°F. To put this temp in perspective properly loaded and inflated tires may get to 160°F and ultra high speed tires such as seen at the Indianapolis 500 may see 200° to 210° but rubber starts to come apart an just a little more than that.


In pic 108 is another view of the same location of melted body cord. If the cord had simply failed due to high pressure the cord would be frayed. Also note the nice circumferential line the failure took. More on that later.


 Moving on to picture 057 note the areas circled in red. An alternate view is seen at the arrow in pic 426. Now if we compare the loss of the ridge that is easily seen in pic 121. What this means is that the upper sidewall was in contact with the road surface for a number of miles and the outer edge of the sidewall "Scuff Guard" raised rib has been completely worn down. What we do not see is the lettering of the "Scuff Guard" worn away so we know that the wear was not due to the trailer being repeatedly parked against a curb.


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Now I am sure some are wondering how I can tell the difference between running a tire at 5 psi vs 0 psi. Well here are some shots from an experiment I ran myself a few years ago.


  This first picture here on the left shows the wear of the upper sidewall that occurred in only 3.9 mi while the tire had a minimum of 5 psi cold inflation. This is a bit like the wear on the RV tire sidewall

The next picture is of the interior of the same tire. You can see the nice circumferential crease/crack that has formed. This tire did not generate enough heat to melt the body cord as I was driving at less than 10 mph for the 3.9 mile test. That crease is at the location up the sidewall similar to where we see the circumferential failure in the "Blowout". Note there is no contact between the inside of the tread and the inside of the tire above the wheel as seen in the RV tire.

If you look at some of the examples shown in the previous post you will note that many show the same nice circumferential failure line.

Here are some examples that I use as ref pictures to help me understand the Root Cause of a tire failure.

Here are pictures of melted body cord, broken body cord and the holes sometimes left when the cord heats up and shrinks as it melts.
I hope this helps you see how easy it is to be mistaken when you think the failure is because of a defective tire when in fact the evidence shows the tire lost air, the Rv continued down the road at normal highway speed and after a few miles the tire "blew out". The only way to have some warning and to protect yourself against this all too often type of failure is to have a TPMS which will warn you as soon as the tire loses 10% of its air.


Bottom Line: I do not think this tire was "possibly defective" or a "crap tire". It did not "fall apart for no apparent reason". It came apart because it lost its air and the operator did not know till too late.