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Old 02-14-2019, 08:21 PM   #1
Tireman9
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"China Bombs"

I continue to see people talking about 'China Bomb" tires. As an engineer, this makes me a bit sad that so many people appear to have such a poor understanding of the difference between "causation" and "correlation".


While it is true that a majority of the tires on RV trailers that fail were made in Asia, and for many folks that meant "China".



But I would ask If 90+% of the tires applied to RV trailers were made in "China" why are you apparently surprised to learn that 90+% of the tires that fail in RV trailer use were made in "China"?


In an effort to make the difference between "causation" and "correlation" a bit easier to understand I have sometimes offered the following example.


If you check with people in prison you will probably find that 90+% have eaten McDonald's fries. So, therefore, it could be concluded that eating those fries can be considered something like a "gateway drug" to breaking the law and ending up in prison. I think we can see that that conclusion is not sound or reasonable but clearly the numbers are similar to what we see in the RV community.



Yes tires in RV Trailer have shorter life than in other applications but major reasons for the higher rate is clearly a combination of the documented very high percentage of RV Trailers with tires in overload/under-inflation as well the clearly identified impact on belt separations due to Interply Shear due to the suspension design of multi-axle RV trailers.
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Old 02-14-2019, 09:01 PM   #2
sourdough
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Quote:
Originally Posted by Tireman9 View Post
I continue to see people talking about 'China Bomb" tires. As an engineer, this makes me a bit sad that so many people appear to have such a poor understanding of the difference between "causation" and "correlation".


While it is true that a majority of the tires on RV trailers that fail were made in Asia, and for many folks that meant "China".



But I would ask If 90+% of the tires applied to RV trailers were made in "China" why are you apparently surprised to learn that 90+% of the tires that fail in RV trailer use were made in "China"?


In an effort to make the difference between "causation" and "correlation" a bit easier to understand I have sometimes offered the following example.


If you check with people in prison you will probably find that 90+% have eaten McDonald's fries. So, therefore, it could be concluded that eating those fries can be considered something like a "gateway drug" to breaking the law and ending up in prison. I think we can see that that conclusion is not sound or reasonable but clearly the numbers are similar to what we see in the RV community.



Yes tires in RV Trailer have shorter life than in other applications but major reasons for the higher rate is clearly a combination of the documented very high percentage of RV Trailers with tires in overload/under-inflation as well the clearly identified impact on belt separations due to Interply Shear due to the suspension design of multi-axle RV trailers.

Tireman, I appreciate your "opinion" on this hotly discussed topic. My thought would be...you must have irrefutable evidence that the rate of failures is due to "overload/under inflation as well as clearly identified impact on belt separations"? Please post that information or obviously it is an opinion.

Interply shear is something that a trailer tire is subjected to, and built for. Now, I agree that some situations can be much harsher on the tire, but to say that is has "clearly been identified" as a major cause of failures on an ST tire must have some corroborating evidence; please post.

My recent failure wasn't due to your above causes...it was a "China bomb" built in the same province and same factory as the other "China bomb" failures I'm aware of...and oddly, buying a set of tires from a different China factory fixed that for me....and others (the original China bombs blew at just over 3000 miles)...the new "China made tires have about 16k on them and running strong". So yes, I have a great understanding of "causation" and "correlation"...but also real life experience in "what is" and "what ain't". BTW, I have both engineers and PHDs in my family that I try to keep in line...
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Old 02-15-2019, 02:13 AM   #3
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The biggest influence on the "China Bomb" dialogue and culture that we see in the recreational vehicle arena is multifactorial.

First, there are definitely quality control disparities between manufacturers, especially when the product originates in Asia. This is more true now than ever before as RV makers are relentless in building business models that prioritize margins over quality. Tire technology has advanced so much in the last 20 years that I feel the rubber under an RV chassis should be just as competent as what's under an automotive vehicle. Again, tire components are picked exclusively by RV designers without much thought to the quality that may or may not be there.

This leads to my second point, lack of effective governance and guidelines with RV tire fitments (up until recently at least). RV manufacturers have only been required to assemble an RV with tires that match the trailer's gross vehicle weight or the combined weight of the axle ratings underneath. As a result, many tire fitments are only supportive of the trailer's GVWR MINUS the tow vehicles's tongue/pin weight.

The trailer I own is a perfect example of an inadequate tire fitment as the GVWR is 7600# and the OEM Trailer Kings were 14" load range C tires rated for 1760# each. Axles were 3500# each.

The tires provided a total capacity of 7040#. If an owner had 10% tongue weight fully loaded, that would require the tires to provide 6896# of weight carrying capacity. The math after this is simple. The total reserve capacity of all 4 tires was only 144# after day 1 of their "born on" DOT build date. By the time those tires were mated to the axles of these Bullet trailers, how much of that reserve capacity was lost? Furthermore, by the time those trailers were delivered to the customer, how much more did the reserve capacity decline? And did a reserve capacity even exist at delivery? Is there such a thing as "negative reserve capacity".

I believe that last year, RVIA manufacturing guidelines changed in a positive direction for all owners in that RV tire fitments are now required to provide 10% reserve capacity of the trailer's GVW. The same 308BHS trailer is sold today with load range D tires, rated at 2040# each. The tires now provide 1320# of reserve capacity assuming a 10% tongue weight.

With the addition of a US made ST radial tire by Goodyear and an ongoing recognition of substandard RV tire fitments, I think the "China Bomb" nomenclature of recent past will be a historical reference in a maturing RV industry. Lessons learned boys and girls.
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Old 02-15-2019, 03:13 AM   #4
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Roger, allow me to be a little crass. (It may not be my only time today) Since you have joined this forum we have been reminded ad nauseum of your engineering experience. Might I ask you to post two items; first is a reference to ONE individual to whom your advice was helpful and two, post a couple pictures of the damage to your RV caused by any tire failure.
Trailer King tires and their associated brands are a very real problem. When the service writer at CW saw the 9K damage on our Raptor his initial response was "We see this all the time. Same brand." Yes, TPMS, 14 months old, perfectly good Florida highway. (Okay, fair highway) STILL blew two in 30 miles.
I promise to be more pleasant in the near future.
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Old 02-15-2019, 05:38 AM   #5
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I started researching RV trailer tires and those used as OEM RV trailer tires in 2002. “China Bomb” is a misnomer.

Here is a case on point, Goodyear Marathon ST tires. Originally built in the USA and used as OEM on various name brands RV trailers including Keystone & Airstream. The owner feedbacks were, various to dismal. Moved production to China, same sort of feedback. Once again back to the USA, same results. Not once were there any recalls for the brand.

RV trailer tire complaints are notoriously anecdotal.

This is a quote from the USTMA. “Over the years, the Recreational Vehicle Safety & Education Foundation (RVSEF) has weighed tens-of-thousands of motor homes and travel trailers in conjunction with RV events. Of the RVs checked by RVSEF, more than 50 percent had loads that exceeded the capacity of one or more tires on the vehicles. Other surveys have noted that many RV’s have one significantly under inflated tire that is at risk of failure.”

In years past I have personally viewed RV trailer certification labels & Tire placards with the following information, or similar. Vehicle certified GAWR 5080#, tires for that certification 2540# at maximum inflation. When using FMVSS standards; that means the maximum load for the axle is 5080# and the minimum load for the tires on each end is 2540#. A good tire engineer could most likely predict the number of miles those tires will degrade and fail when properly inflated and at maximum load capacity.

The number of recalls for ST tires with defects can be counted on one hand.

Can you name a ST tire manufacturer that has said their brand is good for ##### miles?

The automotive tires come with drive, steer, all position and directional tires. They have each been designed to specifications to support their use in those positions. The ST tire is designed as a follower.

If you’re really serious about giving derogatory names like China Bomb to your tire you should do some troubleshooting and give specific information that led you to that conclusion. Tire blow-outs, tread separation failures and excessive leakages are all conditions. Over load, under inflation and even interplay sheer are causes. Proper explanations for them to cause a failure are determinable by experienced and well trained professionals.
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Old 02-15-2019, 07:47 AM   #6
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I must be lucky.

I have a set of 14" Trailer Kings DC: 0916 LR:C that have in excess of 20k miles since June of 2016. With no uneven wear or signs of separation or blemishes.

These are on my 2017 Bullet Premier 29rkpr.

I plan on replacing before this year's season but I think these have served me well. Probably won't replace with this brand though.
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Old 02-15-2019, 07:50 AM   #7
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[QUOTE=CWtheMan;326783]I started researching RV trailer tires and those used as OEM RV trailer tires in 2002. “China Bomb” is a misnomer.

Here is a case on point, Goodyear Marathon ST tires. Originally built in the USA and used as OEM on various name brands RV trailers including Keystone & Airstream. The owner feedbacks were, various to dismal. Moved production to China, same sort of feedback. Once again back to the USA, same results. Not once were there any recalls for the brand.

RV trailer tire complaints are notoriously anecdotal.

This is a quote from the USTMA. “Over the years, the Recreational Vehicle Safety & Education Foundation (RVSEF) has weighed tens-of-thousands of motor homes and travel trailers in conjunction with RV events. Of the RVs checked by RVSEF, more than 50 percent had loads that exceeded the capacity of one or more tires on the vehicles. Other surveys have noted that many RV’s have one significantly under inflated tire that is at risk of failure.

In years past I have personally viewed RV trailer certification labels & Tire placards with the following information, or similar. Vehicle certified GAWR 5080#, tires for that certification 2540# at maximum inflation. When using FMVSS standards; that means the maximum load for the axle is 5080# and the minimum load for the tires on each end is 2540#. A good tire engineer could most likely predict the number of miles those tires will degrade and fail when properly inflated and at maximum load capacity.

The number of recalls for ST tires with defects can be counted on one hand.

Can you name a ST tire manufacturer that has said their brand is good for ##### miles?

The automotive tires come with drive, steer, all position and directional tires. They have each been designed to specifications to support their use in those positions. The ST tire is designed as a follower.

If you’re really serious about giving derogatory names like China Bomb to your tire you should do some troubleshooting and give specific information that led you to that conclusion. Tire blow-outs, tread separation failures and excessive leakages are all conditions. Over load, under inflation and even interplay sheer are causes. Proper explanations for them to cause a failure are determinable by experienced and well trained professionals.

CW, I'm not in the habit of questioning your information....just try to digest it. In this case I feel I have to.

I have many doubts about the paragraph in red being any sort of "definitive" information as to the cause of trailer tire failures. Case in point..."RV events"; what kind of RV "events"? RV show where a trailer is towed from a lot and left on the tarmac for a week - then they weigh the tire/check the pressure? That kind of statistic? "Other surveys" have noted underinflation on at least one tire which was at risk of failure?? What kind of surveys? By who? At risk of failure....of what? Obviously those kinds of statements raise more questions for me than answers - although they are something to think about.


The paragraph in blue leaves more questions. When you explain "causes" vs "conditions" you imply (at least to me) that overload, under inflation and interply shear are THE causes of tire failures. The only causes? I don't think so IMO. There are defective tires, dare I say many thousands, that can/will have the conditions you describe that won't be caused by the list of causes you present.

All that said, I do believe the RV industry has been/was very lax in the fitment of tires to RVs as far as quality and capacity reserves. I have no doubt in my mind that that alone has contributed to many failures along the way. I also have no doubt that there are plants in China, a specific one comes to mind in the Shandong province, that turn out inferior tires - which is not on your list of "causes". Thankfully, from what I've seen lately as new folks question their truck and trailer weights, the reserve capacity has risen on a new trailer which is a VERY good thing.

As far as documented, definitive proof of the causes of ST tire failures, I don't think anything exists simply because that kind of information would not only have to be forwarded to some collection point, it would have to be investigated first. I have a good friend that owns the busiest tire shop in town; I've watched LOTS of blown and flat tires pulled off of cars and trailers. I've never seen one documented on any kind of form and sent anywhere, and I suspect it is like that virtually everywhere. With that observation in mind I can only surmise that any statements relating to "definitive" proof of st tire failures is conjecture or opinion from any party.
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Old 02-15-2019, 09:01 AM   #8
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Quote:
Originally Posted by CWtheMan View Post
I started researching RV trailer tires and those used as OEM RV trailer tires in 2002. “China Bomb” is a misnomer.

Here is a case on point, Goodyear Marathon ST tires. Originally built in the USA and used as OEM on various name brands RV trailers including Keystone & Airstream. The owner feedbacks were, various to dismal. Moved production to China, same sort of feedback. Once again back to the USA, same results. Not once were there any recalls for the brand.

RV trailer tire complaints are notoriously anecdotal.

....
My 1993 Holiday Rambler had Goodyear Marathon ST tires on it. They were recalled in 1994 and the replacements were recalled again in 1996. On the second recall, the Goodyear tire dealer in Alexandria suggested that I install Maxxis tires rather than "risk another recall" by accepting the 1 for 1 exchange. It cost me $8 a tire to "upgrade to Maxxis".

Goodyear is "accused of doing silent recalls" rather than announcing across the board replacement campaigns. Here's one: http://articles.latimes.com/2000/nov/07/news/mn-48936 Seems if you yell and scream, they pay you for your troubles, if you sit quietly while they replace your tires, you pay them for the problems they likely had a hand in creating.

Goodyear also has an enormous amount of litigation pending on one line of motorhome tires that were/are considered inferior for motorhome service.

There may not be any "Goodyear Marathon Recalls" since 2000 when you started following ST tires, but I can attest that Goodyear was replacing an enormous number of Marathon ST tires in the 1990's.
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Old 02-15-2019, 09:46 AM   #9
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I have never called any tire a China Bomb. Why, I beleive CW last paragraph about why they fail is true in most cases. Why, while not a tire engineer, #1 I beleive tires and even more so tires on RV are not properly used and maintained. #2 the ST tires are only built to what could be called minimum standards. If they all over built their products to allow for the MOST RV type person who will never maintain the tire as it should. I am talking about load, speed, age, inflation. There of course would still be failures just like in any tire on any vehicle. But, my opinion there would be less problems.
Until all RVers quit thinking that just because the tire has tread on it it's good for the next trip. There will always be blow outs.
I still see on a daily basis many more passenger vehicles with flats and blown tires on the interstate than RVs. Anyone have a answer for that. I know why, but just asking if anyone else can answer.
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Old 02-15-2019, 09:49 AM   #10
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Go the the Walmart site and look at ST tires and you will see a ZILLION brands of tires no one has ever heard of. Who buys these things?
Supermax
Provider
Trailer King II
Freestar
Greenball
Taskmaster
Trailer King
Goodyear Marathon
Zeemax
Power King
Eco
Nanco
Geostar
Kenda
Loadstar
Ranier
Winda
Wanda
Free Country
Carlisle
Americana
eCustomrim
HiRun

And didn't get through 10 pages of those things with more than 50 pages of trailer tires available for purchase! WHO BUYS THESE THINGS?
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Old 02-15-2019, 09:59 AM   #11
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Tireman, I appreciate your "opinion" on this hotly discussed topic. My thought would be...you must have irrefutable evidence that the rate of failures is due to "overload/under inflation as well as clearly identified impact on belt separations"? Please post that information or obviously it is an opinion.

Interply shear is something that a trailer tire is subjected to, and built for. Now, I agree that some situations can be much harsher on the tire, but to say that is has "clearly been identified" as a major cause of failures on an ST tire must have some corroborating evidence; please post.

My recent failure wasn't due to your above causes...it was a "China bomb" built in the same province and same factory as the other "China bomb" failures I'm aware of...and oddly, buying a set of tires from a different China factory fixed that for me....and others (the original China bombs blew at just over 3000 miles)...the new "China made tires have about 16k on them and running strong". So yes, I have a great understanding of "causation" and "correlation"...but also real life experience in "what is" and "what ain't". BTW, I have both engineers and PHDs in my family that I try to keep in line...

Danny, CWthe Man was nice enough to post the info from NHTSA and RVSEF about 50% of RVs having one or more tire in overload.


I trust you have read THIS post. Re your engineering analysis that indicates "china bomb" is a reason for failure I am wondering why that cause is not included in the Tire Industry Association condition manual approved and supported by Goodyear, Bridgestone, Michelin, Yokohama and a few other tire companies? Why isn't you analysis supported in the book on "Tire Forensic Investigation" by Giapponi?


RE the science behind Interply Shear. I have a number of posts on my blog on that topic but for those not interested in reading that info I provide the following from tire industry research.

Dr. Song's paper on"FATIGUE OF CORD-RUBBER COMPOSITES FOR TIRES."
Here is the abstract.
Fatigue behaviors of cord-rubber composite materials forming the belt region of radial pneumatic tires have been characterized to assess their dependence on stress, strain and temperature history as well as materials composition and construction. Using actual tires, it was found that interply shear strain is one of the crucial parameters for damage assessment from the result that higher levels of interply shear strain of actual tires reduce the fatigue lifetime. Estimated at various levels of load amplitude were the fatigue life, the extent and rate of resultant strain increase (“dynamic creep”), cyclic strains at failure, and specimen temperature. The interply shear strain of 2-ply ‘tire belt’ composite laminate under circumferential tension was affected by twisting of specimen due to tension-bending coupling. However, a critical level of interply shear strain, which governs the gross failure of composite laminate due to the delamination, appeared to be independent of different lay-up of 2-ply vs. symmetric 4-ply configuration. Reflecting their matrix-dominated failure modes such as cord-matrix debonding and delamination, composite laminates with different cord reinforcements showed the same S-N relationship as long as they were constructed with the same rubber matrix, the same cord angle, similar cord volume, and the same ply lay-up. Because of much lower values of single cycle strength (in terms of gross fracture load per unit width), the composite laminates with larger cord angle and the 2-ply laminates exhibited exponentially shorter fatigue lifetime, at a given stress amplitude, than the composite laminates with smaller cord angle and 4-ply symmetric laminates, respectively. The increase of interply rubber thickness lengthens their fatigue lifetime at an intermediate level of stress amplitude. However, the increase in the fatigue lifetime of the composite laminate becomes less noticeable at very low stress amplitude. Even with small compressive cyclic stresses, the fatigue life of belt composites is predominantly influenced by the magnitude of maximum stress. Maximum cyclic strain of composite laminates at failure, which measures the total strain accumulation for gross failure, was independent of stress amplitude and close to the level of static failure strain. For all composite laminates under study, a linear correlation could be established between the temperature rise rate and dynamic creep rate which was, in turn, inversely proportional to the fatigue lifetime. Using the acoustic emission (AE) initiation stress value, better prediction of fatigue life was available for the fiber-reinforced composites having fatigue limit. The accumulation rate of AE activities during cyclic loading was linearly proportional to the maximum applied load and to the inverse of the fatigue life of cord-rubber composite laminates. Finally, a modified fatigue modulus model based on combination of power-law and logarithmic relation was proposed to predict the fatigue lifetime profile of cord-rubber composite laminates."

As you understand Finite Eliment analysis but may not have run the analysis I will offer that the results show that tires on multi-axle trailers are subject to IPS that is 24% higher than an identical tire in motor vehicle service.


Looking forward to learning where I can read your peer reviewed scientific papers so I can correct my obviously flawed understanding of why tires fail.


Have a nice day and happy Camping.
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Old 02-15-2019, 10:35 AM   #12
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Well Golllllyyy! I was planning on a trip to the Oregon coast the end of March.
Now, after reading this thread, I'm not ever moving the trailer again. Too afraid that my interply shearing whatsits will detonate my fitments.
Can the site team come up with a "tire police" or "certified tire engineer" badge/certificate? Seems like we ought to have one?
BTW, I looked all over my trailer and can't find my fitments
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Old 02-15-2019, 11:12 AM   #13
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[QUOTE=sourdough;326802]
Quote:
Originally Posted by CWtheMan View Post
“Over the years, the Recreational Vehicle Safety & Education Foundation (RVSEF) has weighed tens-of-thousands of motor homes and travel trailers in conjunction with RV events. Of the RVs checked by RVSEF, more than 50 percent had loads that exceeded the capacity of one or more tires on the vehicles. Other surveys have noted that many RV’s have one significantly under inflated tire that is at risk of failure.

I have many doubts about the paragraph in red being any sort of "definitive" information as to the cause of trailer tire failures. Case in point..."RV events"; what kind of RV "events"? RV show where a trailer is towed from a lot and left on the tarmac for a week - then they weigh the tire/check the pressure? That kind of statistic? "Other surveys" have noted underinflation on at least one tire which was at risk of failure?? What kind of surveys? By who? At risk of failure....of what? Obviously those kinds of statements raise more questions for me than answers - although they are something to think about.
That subject is written about almost monthly in various tire news publications. I used the USTMA reference because it’s a new PDF revised when the RMA changed its name to USTMA. They represent the entire tire industry.

Sorry for the board term. Here is the RVSEF web site. They are quite active. I’m surprised you’ve not been to an event where they were weighing RVs. They are quite proficient. They were at Quartzsite the two times we have been there. Once when camping at Mackinaw Mill Creek Camping in upstate MI they were there for a huge motor home rally and were also set-up for fivers/TTs.

https://rvsafety.com/
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Old 02-15-2019, 11:23 AM   #14
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Originally Posted by wiredgeorge View Post
Go the the Walmart site and look at ST tires and you will see a ZILLION brands of tires no one has ever heard of. Who buys these things?
Supermax
Provider
Trailer King II
Freestar
Greenball
Taskmaster
Trailer King
Goodyear Marathon
Zeemax
Power King
Eco
Nanco
Geostar
Kenda
Loadstar
Ranier
Winda
Wanda
Free Country
Carlisle
Americana
eCustomrim
HiRun

And didn't get through 10 pages of those things with more than 50 pages of trailer tires available for purchase! WHO BUYS THESE THINGS?
I don't have any idea whether those brands are big sellers for WalMart online (direct to consumer), but one answer to your question is tire shops. I've had a 12x6 enclosed cargo trailer for over 16 years (used for hauling my dirt bikes). Before I got interested in purchasing a toyhauler 2 years ago and started reading these forums and learning more about tires, I would just go into the local shop and say "hi, I need new tires for my trailer, what d'ya got?". They carried several of those brands in your list, and I had a few of them on my trailer.

I've had multiple blowouts on that trailer over the years even though it was never heavily loaded. Knowing what I know now, I attribute those blowouts to tire age. I didn't realize ST tires had a "shelf life" and needed to be replaced even when they weren't badly worn. I was under the impression "they still have plenty of tread left, they're fine!". I know better now.

When we purchased our toy hauler 2 years ago, I immediately replaced the OEM Trailer Kings with Sailuns, watch the pressures carefully, and so far, no problems!
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Old 02-15-2019, 11:23 AM   #15
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Originally Posted by JRTJH View Post
My 1993 Holiday Rambler had Goodyear Marathon ST tires on it. They were recalled in 1994 and the replacements were recalled again in 1996. On the second recall, the Goodyear tire dealer in Alexandria suggested that I install Maxxis tires rather than "risk another recall" by accepting the 1 for 1 exchange. It cost me $8 a tire to "upgrade to Maxxis".

Goodyear is "accused of doing silent recalls" rather than announcing across the board replacement campaigns. Here's one: http://articles.latimes.com/2000/nov/07/news/mn-48936 Seems if you yell and scream, they pay you for your troubles, if you sit quietly while they replace your tires, you pay them for the problems they likely had a hand in creating.

Goodyear also has an enormous amount of litigation pending on one line of motorhome tires that were/are considered inferior for motorhome service.

There may not be any "Goodyear Marathon Recalls" since 2000 when you started following ST tires, but I can attest that Goodyear was replacing an enormous number of Marathon ST tires in the 1990's.

Well by now you must know I did my homework before posting. Here was the results.

https://www.nhtsa.gov/tire/GOODYEAR/...604#complaints
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Old 02-15-2019, 11:32 AM   #16
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Originally Posted by jsmith948 View Post
Well Golllllyyy! I was planning on a trip to the Oregon coast the end of March.
Now, after reading this thread, I'm not ever moving the trailer again. Too afraid that my interply shearing whatsits will detonate my fitments.
Can the site team come up with a "tire police" or "certified tire engineer" badge/certificate? Seems like we ought to have one?
BTW, I looked all over my trailer and can't find my fitments

Jack, It may be a disappointment to some, but I am an actual Tire Design & Quality Engineer with 40 years experience (1969 - 2010) on everything from Truck tires to Indianapolis tires and most in-between. I have owned 5 different RVs and 6 different trailers over the years and have had an ST tire failure on one.
I also am a court recognized "Expert Witness" as it relates to tires and tire failures and was recently cited in the decision on a National Class Action case which we won. I also serve on the Technical Advisory Committee of FMCA as the tire expert, so maybe I do have the appropriate background you are talking about.

It appears I went and hit the hornet's nest on preconceived notions that some held when I started this thread. My intention was to simply point out the problem with jumping to a conclusion not based on data but on the observation that since many trailer tires that had failed were made in "China" the root cause reason for the failure could only be due to the zip code on the mail box for the tire plant or maybe simply because the tire plant was painted blue instead of green.



It is and always has been my objective to try and bring engineering and science to the table but as the saying goes you can lead a horse to water but you can't make them drink.
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Old 02-15-2019, 11:33 AM   #17
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When the service writer at CW saw the 9K damage on our Raptor his initial response was "We see this all the time. Same brand." Yes, TPMS, 14 months old, perfectly good Florida highway. (Okay, fair highway) STILL blew two in 30 miles.

The 2nd tire failure was very predictable. It was severely overloaded as the result of the 1st failure. In reality, all remaining tires are suspect.
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Old 02-15-2019, 02:05 PM   #18
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Originally Posted by Tireman9 View Post
Danny, CWthe Man was nice enough to post the info from NHTSA and RVSEF about 50% of RVs having one or more tire in overload.


I trust you have read THIS post. Re your engineering analysis that indicates "china bomb" is a reason for failure I am wondering why that cause is not included in the Tire Industry Association condition manual approved and supported by Goodyear, Bridgestone, Michelin, Yokohama and a few other tire companies? Why isn't you analysis supported in the book on "Tire Forensic Investigation" by Giapponi?


RE the science behind Interply Shear. I have a number of posts on my blog on that topic but for those not interested in reading that info I provide the following from tire industry research.

Dr. Song's paper on"FATIGUE OF CORD-RUBBER COMPOSITES FOR TIRES."
Here is the abstract.
Fatigue behaviors of cord-rubber composite materials forming the belt region of radial pneumatic tires have been characterized to assess their dependence on stress, strain and temperature history as well as materials composition and construction. Using actual tires, it was found that interply shear strain is one of the crucial parameters for damage assessment from the result that higher levels of interply shear strain of actual tires reduce the fatigue lifetime. Estimated at various levels of load amplitude were the fatigue life, the extent and rate of resultant strain increase (“dynamic creep”), cyclic strains at failure, and specimen temperature. The interply shear strain of 2-ply ‘tire belt’ composite laminate under circumferential tension was affected by twisting of specimen due to tension-bending coupling. However, a critical level of interply shear strain, which governs the gross failure of composite laminate due to the delamination, appeared to be independent of different lay-up of 2-ply vs. symmetric 4-ply configuration. Reflecting their matrix-dominated failure modes such as cord-matrix debonding and delamination, composite laminates with different cord reinforcements showed the same S-N relationship as long as they were constructed with the same rubber matrix, the same cord angle, similar cord volume, and the same ply lay-up. Because of much lower values of single cycle strength (in terms of gross fracture load per unit width), the composite laminates with larger cord angle and the 2-ply laminates exhibited exponentially shorter fatigue lifetime, at a given stress amplitude, than the composite laminates with smaller cord angle and 4-ply symmetric laminates, respectively. The increase of interply rubber thickness lengthens their fatigue lifetime at an intermediate level of stress amplitude. However, the increase in the fatigue lifetime of the composite laminate becomes less noticeable at very low stress amplitude. Even with small compressive cyclic stresses, the fatigue life of belt composites is predominantly influenced by the magnitude of maximum stress. Maximum cyclic strain of composite laminates at failure, which measures the total strain accumulation for gross failure, was independent of stress amplitude and close to the level of static failure strain. For all composite laminates under study, a linear correlation could be established between the temperature rise rate and dynamic creep rate which was, in turn, inversely proportional to the fatigue lifetime. Using the acoustic emission (AE) initiation stress value, better prediction of fatigue life was available for the fiber-reinforced composites having fatigue limit. The accumulation rate of AE activities during cyclic loading was linearly proportional to the maximum applied load and to the inverse of the fatigue life of cord-rubber composite laminates. Finally, a modified fatigue modulus model based on combination of power-law and logarithmic relation was proposed to predict the fatigue lifetime profile of cord-rubber composite laminates."

As you understand Finite Eliment analysis but may not have run the analysis I will offer that the results show that tires on multi-axle trailers are subject to IPS that is 24% higher than an identical tire in motor vehicle service.


Looking forward to learning where I can read your peer reviewed scientific papers so I can correct my obviously flawed understanding of why tires fail.


Have a nice day and happy Camping.

I am not questioning your "engineering" expertise, I question the definitive data that excludes the possibility of a "China bomb" - none has been presented. "Studies", unless performed on the actual failures are then just a basis for conjecture, assumptions and possibilities - nothing is proven by them other than what the data actually shows. To say that more than 1/2 of the RVs at a show had a tire in an overload condition, then jump that actual data, to state the fact that all tire failures are due to overload, underinflation or interply shear, and there are no defective tires from the factory is.....well, a 'fer stretch. IMO the data collected by those that have the failures and then share is far more definitive than studies on good tires. But that's just me.

For me, there is no "hornet's nest" surrounding the "China bomb" nomenclature. It's simply a fact that hasn't been refuted by any statement made in this thread thus far. Whether one chooses to call them a "China Bomb", "Shandong crap" or whatever to simplify addressing them seems OK to me. A "study" on "normal tires" does not disprove their existence IMO.

I know you have your thoughts on the subject and that's fine. We can agree to disagree.
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Old 02-15-2019, 02:30 PM   #19
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Well by now you must know I did my homework before posting. Here was the results.

https://www.nhtsa.gov/tire/GOODYEAR/...604#complaints
Cal, Those results, from what I can see range from 2001 to 2014. There are no recalls listed on that site for Marathon tires in the 1990's. My 1993 HR Marathon tires were recalled twice. The first ones that were installed to "resolve the recall" were recalled about 18 months after installation. The second time is when I installed Maxxis to replace the Marathons rather than install a 3rd set.

Your "homework" may be "spot on accurate" for the time period referenced, but does not include a comprehensive time range for recalls.
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Old 02-15-2019, 06:55 PM   #20
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I am not questioning your "engineering" expertise, I question the definitive data that excludes the possibility of a "China bomb" - none has been presented. "Studies", unless performed on the actual failures are then just a basis for conjecture, assumptions and possibilities - nothing is proven by them other than what the data actually shows. To say that more than 1/2 of the RVs at a show had a tire in an overload condition, then jump that actual data, to state the fact that all tire failures are due to overload, underinflation or interply shear, and there are no defective tires from the factory is.....well, a 'fer stretch. IMO the data collected by those that have the failures and then share is far more definitive than studies on good tires. But that's just me.

For me, there is no "hornet's nest" surrounding the "China bomb" nomenclature. It's simply a fact that hasn't been refuted by any statement made in this thread thus far. Whether one chooses to call them a "China Bomb", "Shandong crap" or whatever to simplify addressing them seems OK to me. A "study" on "normal tires" does not disprove their existence IMO.

I know you have your thoughts on the subject and that's fine. We can agree to disagree.

Looking forward to your presentation of the physical evidence that confirmes "China Bomb" as the root cause of various failures. This evidence would, of course, be of great interest to the engineers that contributed to the TIA Condition Manuals (Passenger, Light Truck & Heavy Truck editions).
Photos or chemical analysis of the claimed "defects" would be most helpful to the tire industry as a whole. Simply making a claim for the presence of a suspect "defect" is not sufficient. Actual evidence is what is needed if one wants to establish the "guilt" of certain tires.


RE RVSEF data. As I understand it, this consists of 10 to 20,000 measurements collected since 1993 at numerous locations across the country. RV owners paid a fee to have their RV weighed. This data corroborates similar data collected by US DOT in relation to the Ford Explorer recall that demonstrated a good portion of the driving public operating at "significant" levels of underinflation. This data is a major portion of why all new cars come with TPMS. During the investigation phase of the Explorer situation well over 10,000 tires were collected and inspected with over 4,000 receiving "cut tire autopsy" level of inspection. So there is data to support that high tire failure rates are directly related to high rates of operation in underinflated/overloaded condition.


I do find your request that I need to prove the negative to reject your claim of the still mysterious "China Bomb" condition a bit telling. If you want to make a claim then you need to present evidence to support the claim. It is not my responsibility or the responsibility of others to disprove your claim.



At this point, until you can provide the physical evidence of your claimed "China Bomb" condition and the data that supports the idea that tires with this condition are prone to failure and those without the "defect" will not fail, I am done spending my time with you on this topic.
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