I just had a tire failure, for no reason

If you follow any RV forums you probably see a statement like this every few weeks. I can tell you that tires do not fail because of some RV-Magic. It comes down to actual Science.

Why do tires fail?

Simple question but as with almost every question about tires, the answer is not a one liner. This post. It's not short but it really isn't technical and I'm sure every reader will understand the concepts.

When looking at why tires fail we need to first exclude the obvious damage caused by external objects i.e. pot holes, curbs, chunks of metal, glass or rock or other trash and junk on the road. Second we'll exclude broken valve bodies, leaky valve cores, valve gaskets, extension hoses, and cracked rims.

What's left will be a structural failure which would almost 100 percent of the time will be either a detachment of different parts or components of a tire one from the other, OR a heat/fatigue failure in the mid sidewall due to driving with extreme low inflation.

Most tires are made up of 20 to 30 different components such as different steels (belts and bead are not the same steel) textiles such as Nylon, Polyester, Rayon, Aramid. Then there are the various different rubber components such as Tread, Sidewall, Innerliner, Steel skim, Wedge, Flippers, Chaffer, base tread, Inserts, and other bits and pieces.

Each component is selected for different reasons and contributes both advantages and disadvantages to the total. Each component must "stick" to its neighbors both in the un-cured and cured state. The interface between two different components is weaker than the individual components but it must hold together through millions of cycles over a 200F degree temperature range.

All would be just fine if a tire were made completely of inorganic materials such as metals, stone or even ceramics. There are numerous formulas for the strength and fatigue limits for these inorganic materials.

The issue with organics (wood, rubber or other materials made from oil such as plastics) is that their strength has a "T" or time function. If you build a bridge of stone, you can calculate the maximum load it can sustain and as long as the structure isn’t changed due to external damage its strength will be the same the day it’s built and 50 years later. If I build a pressure vessel of steel and put 150 psi in it and it doesn’t fail I would have every expectation for it to continue to hold that pressure for decades, again excluding external damage.

However, if I build a pressure vessel of organic materials (a tire) it might hold 150 psi the first day or maybe the first few days but at some point it can fail. This principle is not something many engineers think of today because they don’t design bridges of wood but 100 or 150 years ago when wood was common they learned that a bridge that was strong enough to hold a railroad train to drive across, it could fail if the train parked on the bridge.

I educated some fellow tire engineers about this “T” function when I proved, through lab experiments that it was possible to fail two tire with high pressure above its stated max 18 days after it was initially inflated.

The other condition that affects and changes the “T” in the equation is temperature. Organics experience constant change (loss) in properties as the temperature increases. The rate of change (aging) doubles about every 18 degrees F of increase in temperature, so it's not easy to calculate or predict the time it will take for an organic structure to fail unless you can control the temperature over time.

Bottom line. It’s a combination of temperature (heat) and time that causes tires to fail. A tire that spends its life in Flagstaff, Ariz., could probably last twice as long as a tire that spent its life in Phoenix if all other operating conditions were identical so even knowing the state where the RV was used isn't sufficient.

As the owner of an RV you can significantly affect one factor and that is the heat generated internal to the tire. When you run fast or overloaded or under-inflated you are running hotter. This means you are speeding up the rate of "aging" of your tires and can expect to see a tire fail before it wears out. You can also protect and shield your tires from the heat generated when in direct sunlight while your RV is parked. HERE you can read about an experiment I ran on the benefits of shielding your tires from Sun exposure.

##RVT1048

Why do tires fail?

Simple question but as with almost every question about tires, the answer is not a one liner. Stick with this post. It's not short but it really isn't technical and I'm sure every reader will understand the concepts.

When looking at why tires fail we need to first exclude the obvious damage caused by external objects i.e. pot holes, curbs, chunks of metal, glass or rock or other trash and junk on the road. Second we'll exclude broken valve bodies, leaky valve cores, valve gaskets, extension hoses, and cracked rims.

What's left will be a structural failure which would almost 100 percent of the time will be a detachment of different parts or components of a tire one from the other.

Most tires are made up of 20 to 30 different components such as different steels (belts and bead are not the same steel) textiles such as Nylon, Polyester, Rayon, Aramid. Then there are the various different rubber components such as Tread, Sidewall, Innerliner, Steel skim, Wedge, Flippers, Chaffer, base tread, Inserts, and other bits and pieces.


Each component is selected for different reasons and contributes both advantages and disadvantages to the total. Each component must "stick" to its neighbors both in the un-cured and cured state. The interface between two different components is weaker than the individual components but it must hold together through millions of cycles over a 200 degree temperature range.

All would be just fine if a tire were made completely of inorganic materials such as metals, stone or even ceramics. There are numerous formulas for the strength and fatigue limits for these inorganic materials.

The issue with organics (wood, rubber or other materials made from oil such as plastics) is that their strength has a "T" or time function. If you build a bridge of stone, you can calculate the maximum load it can sustain and as long as the structure isn’t changed due to external damage its strength will be the same the day it’s built and 50 years later. If I build a pressure vessel of steel and put 150 psi in it and it doesn’t fail I would have every expectation for it to continue to hold that pressure for decades, again excluding external damage.

However, if I build a pressure vessel of organic materials (a tire) it might hold 150 psi the first day or maybe the first few days but at some point it can fail. This principle is not something many engineers think of today because they don’t design bridges of wood but 100 or 150 years ago when wood was common they learned that a bridge that was strong enough to hold a railroad train to drive across, it could fail if the train parked on the bridge.

I educated some fellow tire engineers about this “T” function when I proved, through lab experiments that it was possible to fail a tire with high pressure above its stated max 18 days after it was initially inflated.

The other condition that affects and changes the “T” in the equation is temperature. Organics experience constant change (loss) in properties as the temperature increases. The rate of change (aging) doubles about every 20 degrees of increase in temperature, so it's not easy to calculate or predict the time it will take for an organic structure to fail unless you can control the temperature over time.

Bottom line. It’s a combination of temperature (heat) and time that causes tires to fail. A tire that spends its life in Flagstaff, Ariz., could last twice as long as a tire that spent its life in Phoenix if all other operating conditions were identical.

As the owner of an RV you can significantly affect one factor and that is the heat generated internal to the tire. When you run fast or overloaded or under-inflated you are running hotter. This means you are speeding up the rate of "aging" of your tires and can expect to see a tire fail before it wears out.

How old is too old

 I read a comment on an RV motorhome forum:

"I continue to read posts indicating that tires will calendar out, in 5 or 7 or even 10 years. After some searching I have yet to find a technical document regarding tire life expectancy. I'm not interested in sales brochures or salesmen guide lines. I'm looking for a document written by a subject matter expert in the tire manufacturing industry. IMO tire life is more a function of proper storage, inflation, maintenance, environment, and care. I believe a physical inspection by a tire professional is more reliable than an arbitrary date."

So I offered the following:

As an actual Tire design Engineer with 40+ years experience, I believe I can provide some information BUT if you are looking for an answer such as 62 Months 2 weeks and 5 days you are out of luck. It's just not that simple.

Maybe you can tell me, in hours, how long a gal of milk will stay "good". Since you know you can't answer that simple question why do you think the answer for a complex structure such as a tire age should be that simple. Do you think that all 27 basic components age at identical rates?

Most tires fail for one of a couple reasons. You should have read THIS post if you searched on "why tires fail?" I have also covered this in detail in a number of posts on my blog "RV Tire Safety"  But we can cover the topic again.

Polymer Cross Link Density is the property that determines how flexible a piece of rubber is. If it is too flexible or elastic it will not hold its shape. If it is not flexible or elastic enough it will develop microscopic cracks. These cracks will grow with every revolution of a tire and also some will grow simply given enough time.

Heat and time will change the cross link density. The rate of change is not linear but doubles with each increase in temperature of 18°F. This means 4 times if it is 36°F hotter or 8 times if the rubber is 54°F hotter. This is why tires that are on RVs that spend most of their life in Southern Tier states like FL, GA, TX, AZ will fail earlier than tires that spend most of their time in ND, MI, NH, ID, OR. But a tire that spends it life in Phoenix will "die" in maybe 4 years an identical tire that spends it's entire life in Flagstaff may live to 8 years. But there are other factors that can have significant effect on tire life.

 

If we were to put a set of tires on a LT and another identical set on a 4 tire trailer, then load all 8 tires to identical load and inflate to identical level the tires on the trailer may have a life that is 25% to 50% shorter than the tires on the truck. This is due to Interply Shear which is the force in all radial tires at the belt edges that is trying to tear the tire apart from the inside (see "Interply Shear" if you want to see my posts on that topic.

This post is on a Class-C thread but I can guarantee that information published here will be incorrectly applied to information on a TT thread because people do not understand the significant different forces internal to a tire.

Michelin has published a guide on tire inspection which basically suggests at 5 years the tire be inspected inside and out annually and re-applied if no problems are discovered. BUT they still put a MAXIMUM life on the tire as unless you have "X-Ray" vision the structure can have cracks that are not visible on the tire surface, even not visible on the internal air chamber surface.

##RVT1035

Tire "Failed for no Apparent reason" I think not.

OK, as you know I follow a number of RV forums. Here is one that caught my eye. Maybe some can learn this lesson before they end up in big trouble.

 

The post started off with   "Well, I can assure that a tire can blow up for no apparent reason. LT275/70R18 Americus Commercial date code 3518. Truck was shaking a bit. Thought drive shaft. If any of you ever drove a bit heavy truck (I used to drive fire trucks) that sat for a long time and got a flat spot, well drive shaft or flat spot feeling.

Couldn't see anything wrong but decided to take my clunker over to (a local NAPA store) and let them have a look. Its about 15 miles. Missus following. Truck was shaking even worse. Missus said she saw the left front "flapping" (her words) and I queried why she didn't call me so I could pull over and check. Anyway I went to the tire and checked by feeling the inside and there was a definite bulge. So I decided to let that go and went in to the office and BANG! rubber off the inside of the driver side front blew off; about a foot long x 8 inch hunk. Tire still holds air. Always kept those tires aired properly.

Bought four Cooper Discoverer A/T All-Season LT275/70R18 125S Tires. The old Americus tires no longer had my confidence. I praised the Lord I was able to make it over to the NAPA without a blow out on the road.

Michelin's would have been my choice but they are outside what I wanted to spend. I checked Sams Club and the same tires were about $100 more a piece than the Coopers."

I wrote the following: I hope this truck owner and some that are reading this post can gain some knowledge.

Well there clearly was a reason for the failure as tires are not Magic. I do not understand what was meant by "blow up for no apparent reason"  If the owner is saying  that he did not understand the different technical reasons for a tire to fail, I can understand that, but as a minimum people should read and try and understand the information in THIS post as it covers the two main reasons for a tire to fail. I have posted this "Why tires Fail" on at least a dozen different RV forums, but as they say you can lead a horse to water but you can't make them drink.

 

When a tire fails, I strongly suggest that you should make at least a minimal effort to understand the "Why" otherwise the actions you take may not prevent another failure.

Think about getting in a car or truck and turning the key and the vehicle doesn't start. Would you simply replace the battery without confirming the reason it didn't start was because the battery didn't have enough charge? What if you were out of gas? Would replacing the starter motor "fix that problem? Of course not. You may not have thought about it but you already approach "Problem Solving" in a logical manner.

 

Tire failures should be approached in the same way if you want to avoid making the same mistake over and over

The vibration you felt was a significant hint that the tire was in the process of coming apart. Tires simply do not go from having a 100% solid construction to having the components such as the steel belts separate the next instant. 

Here is a more detailed post on why tires might fail.    

Here is a story of a tire inspection I did on a tire that was in the process of coming apart.

 As you can see there were a number of warning symptoms. Some were similar to the symptoms you experienced but failed to understand or act upon. 

 

Luckily you were not driving your truck with a significant load at speed when the front tire finally came apart. That could have been serious. I believe that a little self education can be a significant help in reducing potentially serious problems if you have a tire failure.

##RVT1051

Simple question: Why do tires fail?

In reality, tires fail for a relatively small number of Root Cause reasons that can be discovered, but it does require detailed and sometimes exhaustive investigation. By "Root Cause," I mean the initiating feature or condition that eventually led to the failure. Too often people confuse the tire's ending condition with the initiating or "Root Cause" reason for the tire to end up in the condition they are observing.

For the last few years of my 40-year career as a tire engineer, my primary job duty was to investigate failed tires that had conditions that were hard to understand or provided confusing and sometimes contradictory evidence as to the Root Cause for their condition. With that background, I have developed some guiding principles for the most likely reasons for tires to fail.

These are, in no special order:
1. External Damage. These include punctures, cuts, impacts, wheel and valve failures and similar conditions.
2. Run Low Flex Failure. This is best described by the failure of the tire sidewall due to excessive flexing. The flexing is the result of operation when the tire is significantly under-inflated.
3. Belt & Tread Separations. This is when the belts of a radial tire detach from the body or from each other and/or when the tread rubber detaches from the top belt.
4. Manufacturing Defect. For the purpose of this discussion this would be when components of a tire were not manufactured to intended specification.

The "Why" for some of these are obvious, such as the External Damage category.
Others can be further traced to various contributory reasons.

Run Low Flex Failure This is a more accurate description of what some incorrectly call "Blowout". When a tire looses significant inflation air they flex much more that the body cord can tolerate. Excess heat is generated which can, in extreme cases, result in the Polyester actually melting. I showed examples of what this can look link in THIS post. Polyester is used in most Passenger, ST type and LT type tires. Steel body tires are used on most Class-A RVs, the steel can fatigue. I covered "Zipper" failures and steel fatigue in THIS post.

Belt & Tread Separations occur primarily because the rubber around the belt cords or between the belt rubber and the tread rubber isn't strong enough. Now it can be weak for a variety of reasons. Some might be design, some might be manufacturing and some weakening can be caused by cumulative improper service conditions.

Now let's talk about tires made by a reputable company, i.e., one that has tire stores and dealers with physical stores and sells tires that have a warranty of two or more years.
If this tire is subjected to thousands of miles of lower inflation or higher loading or operation at higher speeds or stored is full sunlight it is reasonable to expect the strength of the belt & tread area rubber to loose a good portion of its strength primarily due to the increased operating temperature of the tire. If this tire is in service on a tandem axle trailer then there is also increased Interply Shear which can overload the belt area rubber. The combination of the above may result in a belt or tread separation.

Another possibility is a Manufacturing Defect. These usually occur in small numbers as tires are built in batches so the substitution of the wrong type of rubber may cause tires to fail. It is important to understand that in almost all cases this type of "defect" usually shows up at early life of the tire. It is also very important to understand that unlike some lawyers, engineers deal in facts and logic. Simply having a tire fail is not in it self proof of a defect but all to often that is the position that those in the legal profession seem to jump to. That approach may result in a nice payout to the lawyer but will not result in product improvement as there has been no determination or identification of the actual initiating "defect".

Finally there is the possibility of a design weakness. Now I do not believe that anyone is intentionally designing tires to fail but this sometimes may occur when the performance goals of the manufacturer are limited to meet the bare minimum for strength and durability and the focus is primarily on low cost. There is no absolute way to identify these tires but I do believe there are indicators when looking for tires that are made to a higher standard of quality and durability.
I would consider a tire company reputable if it had a chain of stores across the country. If the tires carry the name of the manufacturer and have a multi-year warranty the longer the better then they probably have higher durability requirements than those established by DOT.

 For ST type tires I would look for tires with a Speed Symbol of "L" (75 mph) or SLOWER. Now a side point about speed. I did a POST some time focusing on speed and strongly recommend you read it. I do not think I would recommend any tire for general use that does not have a speed rating molded on the sidewall. Few people realize that ST tire loading is based on the assumption of 65 mph Max operation speed

I do hope this post will help some to have a better understanding of what can contribute to tire failure and consider what you can do to lower the chances of having such a failure. 

 

##RVT1049

"Why do so many RV tires seem to be failing?"

 Well, that may seem to be a reasonable question but in my opinion it is based on what is often inaccurate failure analysis. In reality, tires fail for a relatively small number of Root Cause reasons that can be discovered, but it does require detailed and sometimes exhaustive investigation. By "Root Cause," I mean the initiating feature or condition that eventually led to the failure. Too often people confuse the tire's ending condition with the initiating or "Root Cause" reason for the tire to end up in the condition they are observing.

For the last few years of my 40-year career as a tire engineer, my primary job duty was to investigate failed tires that had conditions that were hard to understand or provided confusing and sometimes contradictory evidence as to the Root Cause for their condition. With that background, I have developed some guiding principles for the most likely reasons for tires to fail.

These are, in no special order:
1. External Damage. These include punctures, cuts, impacts, wheel and valve failures and similar conditions.
2. Run Low Flex Failure. This is best described by the failure of the tire sidewall due to excessive flexing. The flexing is the result of operation when the tire is significantly under-inflated.
3. Belt & Tread Separations. This is when the belts of a radial tire detach from the body or from each other and/or when the tread rubber detaches from the top belt.
4. Manufacturing Defect. For the purpose of this discussion this would be when components of a tire were not manufactured to intended specification.

The "Why" for some of these are obvious, such as the External Damage category.
Others can be further traced to various contributory reasons.

Run Low Flex Failure This is a more accurate description of what some incorrectly call "Blowout". When a tire looses significant inflation air they flex much more that the body cord can tolerate. Excess heat is generated which can, in extreme cases, result in the Polyester actually melting. I showed examples of what this can look link in THIS post. Polyester is used in most Passenger, ST type and LT type tires. Steel body tires are used on most Class-A RVs, the steel can fatigue. I covered "Zipper" failures and steel fatigue in THIS post.

Belt & Tread Separations occur primarily because the rubber around the belt cords or between the belt rubber and the tread rubber isn't strong enough. Now it can be weak for a variety of reasons. Some might be design, some might be manufacturing and some weakening can be caused by cumulative improper service conditions.

Now let's talk about tires made by a reputable company, i.e., one that has tire stores and dealers with physical stores and sells tires that have a warranty of two or more years.
If this tire is subjected to thousands of miles of lower inflation or higher loading or operation at higher speeds or stored is full sunlight it is reasonable to expect the strength of the belt & tread area rubber to loose a good portion of its strength primarily due to the increased operating temperature of the tire. If this tire is in service on a tandem axle trailer then there is also increased Interply Shear which can overload the belt area rubber. The combination of the above may result in a belt or tread separation.

Another possibility is a Manufacturing Defect. These usually occur in small numbers as tires are built in batches so the substitution of the wrong type of rubber may cause tires to fail. It is important to understand that in almost all cases this type of "defect" usually shows up at early life of the tire. It is also very important to understand that unlike some lawyers, engineers deal in facts and logic. Simply having a tire fail is not in it self proof of a defect but all to often that is the position that those in the legal profession seem to jump to. That approach may result in a nice payout to the lawyer but will not result in product improvement as there has been no determination or identification of the actual initiating "defect".

Finally there is the possibility of a design weakness. Now I do not believe that anyone is intentionally designing tires to fail but this sometimes may occur when the performance goals of the manufacturer are limited to meet the bare minimum for strength and durability and the focus is primarily on low cost. There is no absolute way to identify these tires but I do believe there are indicators when looking for tires that are made to a higher standard of quality and durability.
I would consider a tire company reputable if it had a chain of stores across the country. If the tires carry the name of the manufacturer and have a multi-year warranty the longer the better then they probably have higher durability requirements than those established by DOT.

 For ST type tires I would look for tires with a Speed Symbol of "L" (75 mph) or faster. Now a side point about speed. I did a POST a little while ago on the topic and strongly recommend you read it. I do not think I would recommend any tire for general use that does not have a speed rating molded on the sidewall.

I do hope this post will help some to have a better understanding of what can contribute to tire failure and consider what you can do to lower the chances of having such a failure.

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Why do tires fail?

Some comments on the general question of tire failures and why they seem to be so prevalent on RVs.

Previously I posted on how tires may be selected by the RV manufacturer. Lowest cost with the least margin of safety allowed by law seems to be the general trend for many manufacturers. We also know that well over half of all RVs that even bother to get weighed have one or more tires overloaded. These facts seem to be something that many want to ignore. Many blame the geographic location i.e. China where the tires were manufactured as the cause of the failures. Some think that the tire mfg intentionally makes poor quality tires. The fact is that tires do not fail for no reason at all. They do not fail because the factory was painted green instead of blue. They fail because their finite life is used up or they suffer some external damage or puncture which lets the air out. Punctures are not always obvious as this one with a 6" piece of aluminum from a broken truck rim poking through the tread.

Some punctures are quite small. So small that you need magnification to see them.

 This puncture resulted a 2 psi per week leak and I only found it after noticing the very slow air loss and the need to add air every week to 10 days.

Impacts do not always result in immediate loss of air. Some tires can run for many miles, days or even weeks and still might not “Blowout”.

 Can you honestly remember every pot hole or curb or piece of road trash you ran over in the last 10 or 20 miles or yesterday or 5 days ago as you pulled into the campground?

 

Valves can fail because the rubber components age-out just like tires can but how often have you replaced the rubber gasket in your metal valves? Do you even have bolt in valves? Standard “snap-in” valves are rated 60 psi Max but since they don’t come out of the wheel immediately after you inflate your tire to 65 psi how many owners assume all is OK for the next 5 years and 40,000 miles?

Valve cores can develop slow leaks if a single grain of sand gets lodged in the valve core seal. How many make sure they have a good o-ring in their metal valve caps, or do they simply use the cheap plastic caps as seen on most cars?

Tires age out. This does not mean that they will fail after 2782 days. It means that after sufficient time has elapsed at elevated operating temperature (which accelerates the aging process in a non-linear and ever increasing rate as the temperature goes up) the strength and elastic properties of the rubber degrade to the point that microscopic cracks that start out tearing molecular bonds apart, grow. The cracks never get smaller. They only grow. The rate at which they grow also depends on the physical properties of the rubber and the properties change with the temperature. Once the cracks grow sufficiently large, the structure starts to lose its ability to retain its integrity and things start to come apart in an ever accelerating manner.

I personally have run tests where I exceeded design range for load and inflation. The tires did not fail for 18 days when the load, inflation, speed and temperature were controlled in a laboratory. This test is repeatable so this is not magic. It is sound science. How many people would relate a sudden tire “Blow-Out” with conditions established 18 days previous?

 I do not intend my comments to mean that there has never been a tire failure that was caused by a manufacturing defect. What I want to show is that simply because you do not find a railroad spike lodged in your tire does not mean there was no reason for the failure due to external causes. It takes years of experience and sometimes hours of detailed examination sometimes including chemical analysis, X-Ray and even Electron Microscope examination to find the real reason for the failure. I know of no tire dealership that has any such equipment or that has provided man-weeks of training in forensic analysis to any of their employees that would allow them to arrive at the real answer of whay a given tire failed.

Why aren't there more recalls of bad RV tires?

In addition to writing this blog, I monitor a number of different RV forums for discussions on tires and related issues. I find that many times I am suggesting to people that they should file a complaint with National Highway Traffic Safety Administration about their tire problems. Many times I get replies asking "Why Bother". While this post focuses on trailer tires the information also applies to other RV applications.

"I get tired of hearing that most ST tire problems are caused by the RV owner. I simply don't believe it based on my own experience. NHTSA; never heard of them, much less knew I could file a complaint. So I asked my tire dealer. She said that they do turn in reports on tire problems themselves and/or turn the tires over to their tire reps for analysis. That went for tires they sold or other brands they replaced. So I don't believe the argument that NHTSA doesn't have enough data to see a trend for ST China bombs. Doesn't make sense if tire dealers are turning in info to them to protect their sales and customers."

Scott I have a number of posts on NHTSA. Here is my take on recalls and filing complaints.

They have a limited budget so must focus on most important first. That means things that can result in death or personal injury. TT only see financial loss so obviously would come last.

While your dealer may have sent information to the tire importer I have noted that many times the volume of tires in a "family" may be low enough to avoid the requirement for data be sent to NHTSA.

in 2014 207 Million passenger tires were sold, 29 Mil LT 18 Mil Truck or 254 Mil tires sold each year where a failure might result in personal injury

According to RVIA data there are 9 Mil RVs on the road but this includes approx 1.1 mil motorhomes so if we have 7.9 mil trailers with say 90% on ST type tires buying a set of 4 tires once every 4 years we are looking at maybe 7 mil St type tires sold each year

So if you were NHTSA where would you spend your research tax dollars? On the quality of 254 Mil tires where there might be injury or on the quality of 7 mil tires with almost no chance of injury?

There have been a few recalls on ST type tires but I am also aware of times when ST tires are not recalled simply because the records are poor as most are imports. In some cases the importer is a small company so does not have the money to do a recall that can cost many million dollars even for a small recall. IMO sometimes a small company would simply go out of business rather than try and handle a large recall.

The RV owners seldom file complaints and many times when they do they do not include the DOT serial so that complaint can not be used in the tally of number of complaints.

+++++++++++++++++++++++++++++++++++++
Here is a reply to another reader:

Tireman, this seems to me to be a big picture economics issue. Is it true that the auto and truck industry does not experience the failure rate or short life that the ST tires experience? If true then the RV tire industry and rv chassis mfgs apparently are not willing to manufacture to the same expectations of the auto industry leading to all the woes that we experience. Look in any parking lot and many of the cars are running on poorly inflated tires. My guess is that these do not fail at the same rate as ST tires. I also have an engineering/QA background and have abused tires for 50 years in racing, towing and with heavy Ag equipment and never seen the failure issues we see with ST tires. I do properly maintain and store my tires, even so I have had 3 failures out of 8 tires in the last three years. Anecdotally I also travel enough to see too many RV trailers on the side of the road with failures. If not for economics, why would ST tires only be made to be rated at 65 mph when we live in a faster world? I try to stay under this for fuel economy but find myself at higher speeds frequently. Impossible to practically operate within rated limits. Is this whole issue because RV mfg do not want to pass on the cost of safe tires? I understand Motorhome tire life is 5 to 7 years and tractor trailer operators get hundreds of thousands of miles on tires. ST tires 2 years? Please explain.

IMO the main reason RV TT mfg do not provide better tire fitment (load capacity) is they sell based on "Bling at low cost". When shopping the RV market you will almost never meet a salesperson who tries to sell based on specifications. Yes tires applied to TT are designed to meet 1970 driving speeds (55 mph speed limit) IMO RV Industry lobby actively opposes any change in requirements that might increase costs by even a few dollars.
Yes ST tire life is MUCH shorter than Passenger, LT or Truck tires.

Universal use of TPMS starting in 2005 on passenger cars has significantly lowered tire failure rates on cars but RVIA (mfg association) does not support TPMS as OE on RVs is one example. They also do not support applying 2002 DOT test requirements on ST type tires so you are stuck with 1970 performance in the 2016 world.

You could write to RVIA at info@GoRVing.com but I have been told that as an industry representative organization they may not be very interested in individual complaints.

If you want to learn more, read some of my posts about NHTSA.

PS While I have done training at NHTSA in Washington DC I do not work for DOT or any Gov agency.

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Why do tires fail? Tire expert has the answers

 As an actual Tire Design and Quality Engineer, I know from my 50 years of tire experience, including 25 with a primary focus on failed tire forensic inspection, that tires fail from two basic causes:

• Low air pressure, and/or
• Long-term degradation of the rubber, usually from excess heat.

Low air pressure

An active leak from a puncture or loose valve stem or valve core is the most common reason. Also, poor or no inflation maintenance contributes to low air pressure as all tires lose pressure at about 1% to 2% a month, excluding the pressure change due to changes in ambient temperature, and can lead to a sidewall flex failure, more commonly called a “blowout”.

The sidewall cord can melt (polyester) or fatigue (steel). Many travel trailer and fifth wheel owners fail to realize that they will never “feel” the results of a tire losing air until it is too late. Then they are surprised when the sidewall “lets go.” The rapid air loss “bang,” even when the tire only has about 10 to 20 psi in it, is a big surprise IF they even hear it. A tire pressure monitoring system (TPMS) can provide warning of air loss, so it is good insurance. A TPMS can easily pay for itself many times over.

Long-term degradation of rubber

The long-term degradation of the rubber at the edges of the belts in radial tires can lead to a belt and/or tread separation. Even if the tire keeps its air, you can have this type of failure, so a TPMS will not provide a warning in this case.

This degradation comes with age, as the rubber is always losing flexibility. Just think of those rubber bands you found in the back of the old desk drawer. Even in cool and dark they got brittle. However, running at, near or above the load capacity of a tire will result in increased heat generation. Increased heat actually can accelerate the aging process with a doubling of the rate with each increase of 18 F. Running a margin of at least 15% between tire capacity and measured load is a good first step. Running at higher speed will also generate excess heat. For ST-type tires, this means faster than 65 mph, no matter the Max speed rating.

Realizing that more than half of the RVs on the road have one or more tires in overload is one main contributor to the high tire failure rate. Simply thinking that a tire will fail because the tire plant building is painted blue rather than green is not logical. But many still have feelings along those lines when it comes to where a tire is made.

Buying the lowest cost “no-name” tires is, IMO, a major contributor to poor results. If the main objective is the lowest cost tire, why would anyone be surprised with short tire life?
Just paying more, however, is no guarantee of better quality. I believe the best tire shopping tool available is comparing warranty and service support.

Can you get a multi-year warranty on the tires? Is it possible to get road hazard coverage? Is there a nationwide network of dealers who stock the brand you are considering? The answer to these questions may provide a better indication of tire quality than the opinion of other RV owners published on the internet.

There are some self-appointed “experts” out there who think that selling tires for a numbers of years qualifies them to make technical pronouncements on tire technology. I would suggest that people review "The Pneumatic Tire"   published by the US DOT before making a claim of being a “Tire Expert”.

 

 

 

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Why inflate Motorhome tires differently than Trailer tires?

Found the following in a thread on an RV owner's forum. This came after there were comments about the advantages of inflating trailer tires to the tire sidewall inflation number but inflating Motorhome tires based on the measured load on the tires.

 "Such a hard concept for most to understand."

As an actual tire design engineer, not just someone that has used a lot of tires or bought or sold a lot of tires, I feel I might have a slightly better understanding of the science behind why tires fail.

I try and make the information easy to understand but I find that many simply refuse to accept the fact that my 40 years experience that includes thousands of failed tire "autopsies" might qualify me to give sound advice.

If you simply look at the experience of three groups of tire users. Excluding punctures or pothold impact breaks.

1. Regular motor vehicles. People get about 40 to 50,000 miles before the tires "wear out"  less than 1% experience tire failures.

2. Class-A and Class-C motorhome users. Many only drive 5 to 8,000 miles a year. It is recommended that starting at 5 years of age, tires be professionally inspected. This does not mean a simple walk around to look at the tread depth but close inspection with good lighting. Maybe even using a pit to allow the inner sidewalls to be inspected. Annual ispections thereafter are recommended and replacement at 10 year tire age "no matter how good a tire looks" This group also has a low structural failure rate not tracable to air leak or impact.

3. RV Trailer users "Towables". Based on numerous reports of higher structural failures i.e. belt/tread separations, and some strange patterns left in lose gravel where a trailer was turned 180 degrees I had some computer simulations run and the numbers provided an explination for the "why" towables have a mush worse structural failure rate. The forces inside the tire structure are significantly higher (+24%) in trailer application (i.e. towables) than in motor vehicle applications This force is identified as Interply Shear and it shows up as trying to separate the top steel belt from the bottom steel belt in radial tires.

While it would be possible for RV Trailer companies to make design changes to trailer suspension to allow for "passive steering" as seen on large cement trucks with a tag axle, I doubt they would go to the expense simply to extend tire life.

While lowering the actual load on a tire in trailer service can lower the Interply Shear force I doubt that it is possible to lower the load by 40 to 50%. One thing trailer owners can do to lower this force is to increase the cold inflation to the tire sidewall "max" Sorry to say you can not reduce the Interply Shear to zero as this is the nature of radial tires.

What is the Root Cause of a tire failure?

 "Root Cause" is the initiating condition or first cause. Someone having a temperature is not a Root Cause or Proof of an infection but is an indicator that there is probably an infection of some sort. A "Blowout" is not considered the Root Cause of a tire failure just the final condition.

In reality, tires fail for a relatively small number of Root Cause reasons that can be discovered, but it does require detailed and sometimes exhaustive investigation. By "Root Cause," I mean the initiating feature or condition that eventually led to the failure. Too often people confuse the tire's ending condition with the initiating or "Root Cause" reason for the tire to end up in the condition they are observing.

For the last few years of my 40-year career as a tire engineer, my primary job duty was to investigate failed tires that had conditions that were hard to understand or provided confusing and sometimes contradictory evidence as to the Root Cause for their condition. With that background, I have developed some guiding principles for the most likely reasons for tires to fail.

These are, in no special order:

1. External Damage. These include punctures, cuts, impacts, wheel and valve failures, and similar conditions.

2. Run Low Flex Failure. This is best described by the failure of the tire sidewall due to excessive flexing. The flexing is the result of operation when the tire is significantly under-inflated.

3. Belt & Tread Separations. This is when the belts of a radial tire detach from the body or from each other and/or when the tread rubber detaches from the top belt.

4. Manufacturing Defect. For the purpose of this discussion, this would be when components of a tire were not manufactured to the intended specification.

The "Why" for some of these are obvious, such as the External Damage category.

Others can be further traced to various contributory reasons.

Run Low Flex Failure This is a more accurate description of what some incorrectly call "Blowout". When a tire loses significant inflation air they flex much more than the body cord can tolerate. Excess heat is generated which can, in extreme cases, result in the Polyester actually melting. I showed examples of what this can look like link in THIS post. Polyester is used in most Passenger, ST type, and LT type tires. Steel body tires are used on most Class-A RVs, the steel can fatigue. I covered "Zipper" failures and steel fatigue in THIS post.

Belt & Tread Separations occur primarily because the rubber around the belt cords or between the belt rubber and the tread rubber isn't strong enough. Now it can be weak for a variety of reasons. Some might be design, some might be manufacturing and some weakening can be caused by cumulative improper service conditions.

Now let's talk about tires made by a reputable company, i.e., one that has tire stores and dealers with physical stores and sells tires that have a warranty of two or more years.

If this tire is subjected to thousands of miles of lower inflation or higher loading or operation at higher speeds or stored is full sunlight it is reasonable to expect the strength of the belt & tread area rubber to lose a good portion of its strength primarily due to the increased operating temperature of the tire. If this tire is in service on a tandem axle trailer then there is also increased Interply Shear which can overload the belt area rubber. The combination of the above may result in a belt or tread separation.

Another possibility is a Manufacturing Defect. These usually occur in small numbers as tires are built in batches so the substitution of the wrong type of rubber may cause tires to fail. It is important to understand that in almost all cases this type of "defect" usually shows up in the early life of the tire. It is also very important to understand that, unlike some lawyers, engineers deal in facts and logic. Simply having a tire fail is not in itself proof of a defect but all to often that is the position that those in the legal profession seem to jump to. That approach may result in a nice payout to the lawyer but will not result in product improvement as there has been no determination or identification of the actual initiating "defect".

Finally, there is the possibility of a design weakness. Now I do not believe that anyone is intentionally designing tires to fail but this sometimes may occur when the performance goals of the manufacturer are limited to meet the bare minimum for strength and durability and the focus is primarily on low cost. There is no absolute way to identify these tires but I do believe there are indicators when looking for tires that are made to a higher standard of quality and durability.

I would consider a tire company reputable if it had a chain of stores across the country. If the tires carry the name of the manufacturer and have a multi-year warranty the longer the better then they probably have higher durability requirements than those established by DOT.

For ST type tires I would look for tires with a Speed Symbol of "L" (75 mph) or faster. Now a side point about speed. I did a POST a little while ago on the topic and strongly recommend you read it. I do not think I would recommend any tire for general use that does not have a speed rating molded on the sidewall. Few realize that ST tire load formula is based on a 65 MPH max operation speed.

I do hope this post will help some to have a better understanding of what can contribute to tire failure and consider what you can do to lower the chances of having such a failure.

 

Over the next few weeks I will be posting pictures of tires with different conditions and I will identify what was discovered with a detailed inspection and identified as the most likely Root Cause.  Just to whet your appetite here is a video showing at time 1:12 a 

tire that was initially suspected of having some "Defect".  The physical evidence that proves what the Root Cause was can be seen in the video if you look closely and understand what you are seeing.  If you think you know the answer post it in the comments and the first 5 people to get the answer right with get their name published in my next post. Along with bragging rights.

##RVT1052

 

Why do radial tires fail when overloaded or underinflated?

 I have a number of posts here on the topic of why tires fail. There are also more than 16 posts that mention "separation" or more accurately a "Detachment", as a reason or contributor to a tire failing. But maybe, some readers want more a scientific explanation.

 

This graphic is a computer-generated color depiction of the relative heat generated internally in a tire as it is driven down the road. Light blue is the coolest area, and red is the hottest.

When tires crack

I have covered the "artificial aging" of rubber in several posts. Basically, the molecular cross-link density increases, which can be thought of as stiffening and less flexibility. When rubber loses its flexibility, the molecular bonds crack. As more bonds crack, these cracks join up until they can be seen with the naked eye, as pointed out with the yellow arrows in the picture below.

 

 When tires develop these larger cracks, they simply grow over the next hundreds or thousands of miles, as seen in the next picture.

"Free-Spin Inspection"

Tires with these larger cracks can be identified by doing a "Free-Spin Inspection," as covered in detail in this post on how I inspect my tires.

When doing a "Free-Spin Inspection", If you discover the out-of-round or side-to-side movement as seen in the video in the above post, I strongly suggest you have the tire inspected by your tire dealer for that brand tire, or simply replace the tire if it is more than 3 years old.

By the way, the steel belts do not "slip". They are no longer attached as part of the structure of a radial tire.

 

I hope this helps understand the situation. 

 

Is there a specific "Safety Margin" on tires?

Read a question on tire "Safety Margin" 

I pointed out that the term "safety" margin really doesn't apply to tires but a "durability margin" might be a better way to think about tires.

Tires seldom, if ever fail as soon as they are run 10% overloaded or run 20 psi low or 10mph over their stated speed rating.
Damage is cumulative and I don't know of any automotive parts that "repair" themselves. In some mechanical parts the damage is in the form of accelerated wear. For a moment think of running your engine low on oil. Will the engine fail if you run it 5% low or 20% low or 80% low on oil? In how many miles? I don't know the specific answer to the number of miles based on how low on oil you are. Does the fact that you might not have an immediate engine failure from running 50% low on oil mean it is OK to do that?

In tires, the damage starts at the molecular level with chemical bonds breaking (cracking) which can grow and may become microscopic in size and eventually might result in cracks that grow large enough for the structure to fail. i.e. a belt separation.

Overload or low inflation or over-speed, lets call these damaging events, can each initiate or contribute to an accelerated growth of these "cracks". In rubber there is both an initiation phase and a growth phase.

It is conceivable for tires to tolerate "X" level of damaging event for many thousands of miles and the tire never "initiates" a crack but also there can be a single damaging event such as hitting a pot-hole of a certain size, depth, length, angle of incidence and speed that is the "initiation" event and this results in a belt separation 5 miles or 20,000 miles later, with the variation be the result of different growth rates. This was covered in detail in my blog in Jan 2020. I examined a Tire Industry technical paper on tire forensics and impact damage that identified a 100% correlation between impact damage (such as you might get hitting a pot hole) and belt separation failure.

Many times I read reports from RV owners saying..."I was driving 55 mph down the Interstate and had check the air just an hour previous and was not overloaded when the tire failed for no reason." Sorry but there is always a reason. That reason might be because of the speed, load, inflation road surface, i.e. damaging event, that the tire was driven on 1,000 miles previous to the actual failure.

Forensic tire analysis is a very complex science and there are very few engineers that have the decades of experience it takes to accurately identify the Root Cause of tire failure. I dare say that each major tire company has a handful of engineers capable of correctly identifying the actual root cause of a tire failure 70% of the time. While they may not be able to identify the actual Root Cause they probably have been trained and have enough experience to know if the tire should be "adjusted" as a "customer satisfaction" case but maybe only one engineer that can properly identify 90% of tire failures and be able to issue a technical "white paper" offering the evidence to support their detailed opinion of the originating root cause for the eventual failure. Too often there is too much missing evidence or accurate reporting to tire operation history for anyone to identify the reason why each and every tire failed. 

Since learning all the important facts of the tire's operating and life experience it is very difficult to be able to  identify the reason for every failure. Even if there is physical evidence of the tire hitting a pot hole you can see in the data of the Jan 2020 blog post that you still can't provide a reliable answer such as. You hit a pot hole 5,678 miles ago and that is why your tire failed.

Back to the question of "Safety Factor or Margin". All tires sold for use on US public highways are to meet a series of tests such as speed, load endurance, staying on the wheel with low inflation etc. Tire companies also have their own minimum performance standards that tires are suppose to meet. Tires are not graded such that they pass 85% of the tests or that 90% of all tires made must be capable of passing all the tests. The laws for tire safety are written such that 100% of the tires sold must be capable of passing 100% of the tests. 

Each tire company tests tires beyond the minimums and using statistical data analysis they can predict that the performance required on any individual test tire such that 99.96% or some similar number, of all tires made will be capable of passing the DOT testing when new. Tire companies have whole departments constantly looking at test tire results and result variation in an effort to be confident they are making good tires.

What tire companies can't do is predict how much any individual RV owner will overload or under inflate their tires so it is impossible to come up with some specific "margin" of acceptable overload because the other factors such as speed, ambient temperature during operation and level of under-inflation are unknown and too variable to allow prediction of durability.

##RVT972

Why do trailer tires fail more often than tow vehicle tires?

Here is the question posted on a travel trailer forum.
Why so many trailer tire failures and so few, if any, tow vehicle tire failures?

This post could be considered Part 2 of my post of last week. 

The primary reason IMO is staring everyone in the face and the information is molded onto the tire sidewall so you do not need to be an Einstein, but almost everyone chooses to ignore the science so they can save a few bucks.

Fact: Tire load capacity is a function of air volume (tire size) and inflation pressure. This is well established and is confirmed by every Load & Inflation chart printed. Increase size or increase pressure and you increase load.

If we all drove around on tires with LT level sizing and inflation there would be almost no failures other than those caused by road hazard or punctures.

BUT
People want softer ride, better fuel economy and lower cost so alternatives were introduced into the market.

LT tires can be considered the standard for tires designed to carry load at highway speeds.

P type tires have a higher load capacity than identical size LT tire but if you check the actual load on most car tires, you will see they have 15% to 25% or more "Reserve Load" capacity (more capacity than needed). Inflation is set for cars based not on load but ride, handling and fuel economy. You also know that P tires must have their load capacity de-rated when P tires are used in truck, SUV or trailer application. When P type tires are run with zero reserve load you will probably get more failures. (See Ford Explorer crashes.)

ST tires have a higher claimed load capacity than LT tires and TT companies use the smallest (lowest cost) tire that can, most of the time, meet the specification for load.

How then is it that ST tires are rated to carry more load?
The load formula for ST tires is based on a 65 mph Max operation speed and an expected shorter life. The formula was developed back when bias tires that wore out at less than 15,000 miles were the norm

Since 1990 when ST tires were still "Alpha" sized ( H78-15ST) the load formula has not been changes as far as I can determine.

The science indicates that if you want tire durability on your trailer as you get on your truck maybe you need to consider running the same type tires i.e. LT type and of course that means you also need to use LT Load & Inflation limits.

Here is some info I posted Sept 14 2011

"Here are some facts from the Tire & Rim Association industry standards book 

P235/75R15 105S (Standard Load -35 psi @ max load)
2028# 35 psi 112mph on a Passenger car
1844# 35 psi 112mph on a SUV or P/U or trailer (no Dual)

LT235/75R15 LRC
1512#single 1377# Dual 50 psi 85mph

ST235/75R15 LRC
2340#single 2040# Dual 50 psi 65mph"

NOTE I did not mention the actual load on a tire but only the specified max. Weight data indicates many TT have one or more tire in overload.

Do not do this to your RV tires

 

Do not bleed down your RV tire pressure because you think it will “explode” if you exceed the PSI number molded on the tire sidewall.

Almost every week I see posts on one or more of the various RV forums where people say they limit the PSI in their tires. Sometimes they say why, as in “to prevent a blowout.” Sometimes they do not say why, but their reasoning behind this practice is clear to me.

It appears that many people incorrectly believe that exceeding the “PSI” number molded on the tire sidewall is going to result in tire failure and explosion.

It may help to let people know about some of the testing that tires undergo during the development phase.

First some background

The “Max Inflation” statement on your tire sidewall really is the inflation associated with the Maximum Load capacity. If you actually read your tire sidewall, you will see that is what it says. So the number of PSI is really the minimum needed to support the stated load.

It is important to understand that we are always talking about the “cold” inflation and not the inflation of a tire that is running down the highway or has been in direct sunlight or driven on in the prior couple of hours. “Cold” inflation does not mean the tire needs to be refrigerated. It means the tire is at the prevailing ambient (surrounding) temperature.

Tire pressure monitoring systems

With the introduction of aftermarket tire pressure monitoring systems (TPMS) that report both tire pressure and the temperature of the sensor, people are now being exposed to information they have no previous experience with. They see tire pressure rising as they drive down the highway. Some may see a 10% to 20% rise in pressure from the pressure they set their tires to just a half-hour earlier. This increase is a cause for concern, not because they had any working knowledge of tire operating temperature or pressure, but simply because the pressure was higher than they expected.

What not to do

A few people have decided that they need to bleed down the high pressure because they thought the pressure number of the tire sidewall was the maximum it could tolerate. Of course, the action of bleeding down the hot pressure was exactly the wrong thing to do, as that meant that the tire would no longer be operating at the pressures expected by the tire engineer when they originally designed and tested the tire specification.

Obviously, this raises the question of how much pressure a tire can tolerate before the owner should be concerned. Well, I am going to give you some numbers, but these are only examples. I cannot speak for every tire company’s process or specifications. But if we start with a few guidelines, I think you can get comfortable and, hopefully, you will believe that tire design engineers do have a reasonable idea of what they are doing.

First off, we are only going to discuss regular production street tires that have passed DOT testing. The numbers I will use would basically be seen on new tires. I cannot advise on a tire’s capability after it has been damaged or run for tens of thousands of miles. Damaged tires can fail when reinflated, as seen in this video of a 22.5-size tire.

This video was made to show that welding on a wheel with a tire still mounted can result in a tire failure. Note the pressure at failure.

 

Tell service person if you drove on under-inflated tire

If your tire suffered a puncture and you drove any distance with the tire underinflated, you may have permanently damaged the body cords. That is why you should always tell the tire service person that you drove on the under-inflated tire so they know to use a cage or other restraining safety equipment. Age and miles can reduce the strength of any tire, but we do consider this degradation when approving a design.

Another consideration is the availability of high-pressure air. Most home compressors or those that supply air to hoses made available to consumers have an upper limit of about 150 PSI. Therefore, we don’t expect any consumer to have access to or to use industrial air pressure, which can be 400 PSI, or even special inflation units as used on aircraft tires.

Basically, many tires are tested to 300% to 400% of their rated inflation, or above 200 PSI, whichever is lower. I had a number of tires that could contain over 300 PSI when new. If they had been damaged, however, the same tire might fail at less than 200 PSI. But I also never, in my 40 years as a design engineer, saw a tire fail from normal pressure increase—and I was involved in the testing and evaluation of thousands of tires.

The bottom line

The bottom line is: Please do not bleed down your hot inflation pressure. You should ONLY set and adjust inflation when the tire is cool and at ambient temperature. Doing otherwise MAY result in you having a failure days or weeks later because you were running lower pressure than what was needed for the tire load you were applying.

Also, unless you have damaged your tire, it is unlikely to “explode” simply by adding 10% more cold air pressure.

 

 

 

 

 

 

Tire Recalls

I have seen a number of posts on various forums of complaints about what is believed to be a failure of a “defective” tire. What I have not seen is any mention of anyone having bothered to provide details and information on what the defect is and a statement that they send the data to the US Dept Of Transportation. I have to wonder why people think there might be some government action when there is no information going to the government complaining about what they feel is a defective tire.

You can review the current tire recall list from the National Highway Traffic Safety Administration HERE.

NHTSA is the part of DOT that is responsible for collecting complaint information and doing the appropriate investigation. If there is data developed that would support some action such as a recall, NHTSA is the agency that can order the action. Before a tire might be recalled there is list of “complaints” accumulated and you can review that information HERE.

You file complaints HERE.

It is important to remember that just because someone may have had a tire failure and complained, that does not automatically mean there will be a recall. Many times there are contributing reasons for an individual tire to fail. Most of these contributing reasons are not part of a design or manufacturing trend which would affect a group of tires.

I can recount how my work as a Quality Investigation Engineer resulted in a recall of 4,900 tires when I discovered what was a manufacturing error. This sounds like a big number but in fact the data we assembled identified there were fewer than 150 tires total that had the problem. The reason the number grew is that tire recalls are done based on DOT serial, which as you know includes the week of production. So even though we were able to confirm the problem was caused by a single skid of material being used in the incorrect part of the tire, the entire weeks production had to be recalled. In this case none of the tires had made it to individual customers as the problem was discovered so quickly the tires were either in the warehouse or on vehicles still at dealer lots.

The reason I am telling you this is to show how the system works. A problem is discovered. An investigation is done. Sometimes by NHTSA based on the complaints received from the field and sometimes by the tire manufacturer with their in house quality department. If tires are to be recalled then the formal procedures and laws must be followed.


I have advised a number of people who complain about a tire failure that if they do not file a complaint there is no way there will be a recall or even an investigation. I do note there is a general tendency for many on some RV forums to brand all tire failures as being caused by “defective” tires but based on the pictures I have seen, I remember only one example of the failure that might have been caused by a design or manufacturing problem but since these failures were isolated to a single RV it is more likely the failures were service related.

Can I categorically state that there are currently no defective tires in the field? No I cannot.

However based on my experience of personally inspecting thousands of tires identified as "defective" by self proclaimed experts, the facts are that most tires fail because they are under inflated, overloaded, improperly repaired or suffered a road hazard, impact or even vandalism.

On a personal note I have to wonder why so many in the RV field are quick to blame a tire failure on the country of origin, tire manufacturer or complain when tires need replacing after many years of service and some abuse, while at the same time are willing to spend many tens or hundreds of thousands of dollars on an RV that has such poor quality that no one is willing to stand behind or provide a 100% bumper to bumper warranty of the product design or manufacturing for more than a few months.

I have offered and continue to offer to do a detailed inspection of failed tires and to issue an un-bias report of my findings but too often the most I get is a slightly out of focus and improperly lit photo of the subject tire with no DOT serial and documented loading and service speeds.

I will be offering, in future posts to my blog, examples and information on impacts and road hazards with photographs showing sidewall "bubbles" as well as proof of the tire being damaged in service.

If you have questions about a suspect tire “defect” I will be happy to talk with you if you attend my Tire Basics for the RV Owner at FMCA Family Reunion in Madison, WI the end of August or the Gypsy Journal Rally in Celina, OH the end of Sept.