Why tires fail the answer from tire engineer

[Tireman9]

Tires fail from two basic causes.

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

Low pressure (active leak from puncture or loose valve stem or valve core are most common reasons) can lead to a Sidewall Flex failure or more commonly called a "Blowout". The sidewall cord can melt (polyester) or fatigue (steel). Many TT owners fail to realize that they will never "feel" the results of a tire losing air till it is too late and 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. [moderator edit] A TPMS can provide warning of air loss so is good insurance and can easily pay for itself.

The long-term degradation of the rubber at the edges of the belts 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. This degradation comes with age as rubber is always losing flexibility. Just think of those rubber bands you found in the back of the desk drawer. Even in cool and dark they got brittle. HOWEVER, running at or 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 each increase on 18F. Running a margin of at least 15% between capacity and the measured load is a good first step. Running at a higher speed will also generate excess heat.

Realizing that over half of the RVs on the road has one or more tire or axle 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.

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 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?

[ctbruce]

All good points. Thanks for sharing.

[Snoking]

I will also argue that ST tires with an A/S tread design have been ripping themselves apart for many years in tight maneuvers. You will notice that GY with new Endurance ST has gone to a less aggressive tread pattern. Chris

[Benny]

Thanks, for your previous information. As a tire engineer, is there any reason to use ST tires over LT for my 14,000 5th wheel.

[Tireman9]

Thanks, for your previous information. As a tire engineer, is there any reason to use ST tires over LT for my 14,000 5th wheel.


I can think of many reasons to run ST type.


- The RV company didn't leave enough room for physically larger tires


- You don't want to buy wheels with higher inflation capacity


- You like buying tires with shorter life because you want to be able to drive the speed limit posted for cars


- You don't want to make the effort to learn the actual load on each tire and to then search for a non- ST tire with sufficient load capacity to support the heaviest loaded tire position.


(Sorry for the sarcasm):flowers:

[Benny]

I am not sure I understand your sarcasm. My question was sincere. On these forums many recommend various LT tires over ST. It is because I have researched the specifications on the tires and axels on my 305RL that I asked my question. I do not have more than 10% difference between load and tire specs. The max speed listed is only 65, that is too low for safe highway speeds. I have purchased the ford Internal TPMS units and I have room for a taller tires, available on my 16 inch wheels. If an LT with better specs will be safer in my upcoming trip across Alaska then $100 more a tire is acceptable. BTW I maintain the air pressue on all ten tires. What I can't seam to find is where in the specs ST are superior to LT.

[Snoking]

If you have 6k axles, the best tire you can run is thichelin XPS Rib or Bridgestone Duravis R250. If you wheels are rated to 110 pounds then the Sailing S637 LRG comes in two 16" sizes. All of these tires are steel ply tires, and are good for 6-8 years. Chris

[sourdough]

I am not sure I understand your sarcasm. My question was sincere. On these forums many recommend various LT tires over ST. It is because I have researched the specifications on the tires and axels on my 305RL that I asked my question. I do not have more than 10% difference between load and tire specs. The max speed listed is only 65, that is too low for safe highway speeds. I have purchased the ford Internal TPMS units and I have room for a taller tires, available on my 16 inch wheels. If an LT with better specs will be safer in my upcoming trip across Alaska then $100 more a tire is acceptable. BTW I maintain the air pressue on all ten tires. What I can't seam to find is where in the specs ST are superior to LT.

Benny, you are being drawn into the "ST vs LT" tire conversation by those that have biased views; do your due diligence. There is a reason there is a differentiation between tires made to carry large loads on fixed axles, twist and turn as they are maneuvered etc. Some believe, and at times in the past were probably correct, that ST tires just didn't "measure up" to the construction standards of an LT tire. Those times have changed. ST tires were "trailer" tires. They were placed on a 16' flatbed, the old 12' enclosed side utility trailer etc. They were used on RVs back when and the units were much smaller. As times have changed and the trailers have gotten larger, much larger, the ST tire requirements 1) lagged far behind the evolution of the trailers they were being put on and 2) tire requirements for those trailers failed everyone as well.

That was then; remember the Goodyear Marathon? Over the last many years we have endured the proliferation of the China Bombs; cheaply made tires that managed to meet ST tire requirements (maybe) but made with the poorest of components and no quality control. So, many looked to LT tires as an alternative to give them a better tire, not a better towing tire, but one that they felt was "stronger" or "tougher".

Now, ST tire manufacturers have "gotten much smarter" and started providing tires that can actually provide excellent service for the ST rating. The old days of "LT tires are superior because STs are poorly made", "aren't designed properly" etc. are gone. There IS a difference in the construction of the tires; carrying an RV with 10-15k just sitting on the tires, scrubbing harshly any time the trailer is turned etc. requires a different construction and rubber compound than an auto tire made to carry a regular vehicle. Just look into the zillions of rubber compounds and material construction for the endless variants of tires.

Long post but you are sincerely looking for guidance and thoughts on your tires, I am sure without "sarcasm". I am not biased either way. I use LTs on my trucks/SUVs, I use STs on trailers because that is what is recommended for them (mine). Whatever you choose make sure that the tire has plenty of load capacity to provide a significant reserve above your load weight.

[rhagfo]

Benny, you are being drawn into the "ST vs LT" tire conversation by those that have biased views; do your due diligence. There is a reason there is a differentiation between tires made to carry large loads on fixed axles, twist and turn as they are maneuvered etc. Some believe, and at times in the past were probably correct, that ST tires just didn't "measure up" to the construction standards of an LT tire. Those times have changed. ST tires were "trailer" tires. They were placed on a 16' flatbed, the old 12' enclosed side utility trailer etc. They were used on RVs back when and the units were much smaller. As times have changed and the trailers have gotten larger, much larger, the ST tire requirements 1) lagged far behind the evolution of the trailers they were being put on and 2) tire requirements for those trailers failed everyone as well.

That was then; remember the Goodyear Marathon? Over the last many years we have endured the proliferation of the China Bombs; cheaply made tires that managed to meet ST tire requirements (maybe) but made with the poorest of components and no quality control. So, many looked to LT tires as an alternative to give them a better tire, not a better towing tire, but one that they felt was "stronger" or "tougher".

Now, ST tire manufacturers have "gotten much smarter" and started providing tires that can actually provide excellent service for the ST rating. The old days of "LT tires are superior because STs are poorly made", "aren't designed properly" etc. are gone. There IS a difference in the construction of the tires; carrying an RV with 10-15k just sitting on the tires, scrubbing harshly any time the trailer is turned etc. requires a different construction and rubber compound than an auto tire made to carry a regular vehicle. Just look into the zillions of rubber compounds and material construction for the endless variants of tires.

Long post but you are sincerely looking for guidance and thoughts on your tires, I am sure without "sarcasm". I am not biased either way. I use LTs on my trucks/SUVs, I use STs on trailers because that is what is recommended for them (mine). Whatever you choose make sure that the tire has plenty of load capacity to provide a significant reserve above your load weight.

Sourdough, sorry to disagree, but ST tire are built to a lower standard. Their newer increased speed ratings are due to use of magic speed rating dust.
I have stated it many times before Semis don’t have special ST tires for trailers, all tires have the same carcass, LT’s work well on 5er with a GVWR of about 12,500#.

[Tireman9]

I am not sure I understand your sarcasm. My question was sincere. On these forums many recommend various LT tires over ST. It is because I have researched the specifications on the tires and axels on my 305RL that I asked my question. I do not have more than 10% difference between load and tire specs. The max speed listed is only 65, that is too low for safe highway speeds. I have purchased the ford Internal TPMS units and I have room for a taller tires, available on my 16 inch wheels. If an LT with better specs will be safer in my upcoming trip across Alaska then $100 more a tire is acceptable. BTW I maintain the air pressue on all ten tires. What I can't seam to find is where in the specs ST are superior to LT.




OK sorry for sarcasm


LT tires do have more difficult tests to pass DOT requirements. Some consider that as meaning LT tires are better than ST.


ST tire load capacity is higher than LT tires Some consider that makes them better.


ABout the only yardstick that we can use once we have confirmed the tire load capacity of the tires we are considering is to compare warranties. Especially if you can get a Road Hazard warranty which means there is no exception for getting a warranty replacement.


There is no way for me to know all the possible warranties different dealers can offer so you will need to do the shopping yourself.


So knowing the load capacity you need you can look up the load capacity and inflation of LT tires. Then get on the phone.


Hope that helps.

[Tireman9]

If you have 6k axles, the best tire you can run is thichelin XPS Rib or Bridgestone Duravis R250. If you wheels are rated to 110 pounds then the Sailing S637 LRG comes in two 16" sizes. All of these tires are steel ply tires, and are good for 6-8 years. Chris






Based on what I have seen and reports I have read the above makes sense.

[Benny]

That does help.

[CWtheMan]

That does help.


Depends on your point of view and adherence to tire industry standards and safety.


Michelin will not knowingly replacer original equipment ST tires with any of their LT tires. The link below supports that statement.


https://www.michelinman.com/US/en/help/how-to-choose-tires.html#tab-4

[CWtheMan]

If you have 6k axles, the best tire you can run is thichelin XPS Rib or Bridgestone Duravis R250. If you wheels are rated to 110 pounds then the Sailing S637 LRG comes in two 16" sizes. All of these tires are steel ply tires, and are good for 6-8 years. Chris


There is an added reason why that will no longer happen with the LRE 16" XPS & R250 tires. They cannot provide the 10% of load capacity in reserves above the axle rating as required in the RVIA recommendations.

[Snoking]

There is an added reason why that will no longer happen with the LRE 16" XPS & R250 tires. They cannot provide the 10% of load capacity in reserves above the axle rating as required in the RVIA recommendations.

That would only apply to new trailers and their OEM tires.

[jadatis]

Why are there ST tires of same sises and loadrange,as LT tire, with higher maximum load then the LT tire.
Its because ST tire then is calculated in maximum load for lower speed, mostly 65mh, even if they give N speedrating for 87mh.
Lower speed means less cycles a second so less heatproduction a second.
So the tire can have more deflection so more heatproduction a cycle.
With same pressure this means more load to carry .
But this brings overheating border closer, a bit to high load or speed, or a bit to low pressure, gives already more heatproduction then can be cooled down, and rubber goes above a temp at wich it damages ireversible, then time will do the rest. The beginning crackes then crack further at every next cycle, until at the end, mayby even after 3 years, the tire is that much damaged that it blows or treath comes of.

Thats why it is best to give the tire a deflection the same as same LT tire would be calculated for. Mostly this means a pressure above what is allowed for that tire.
An LT tire nowadays pressure behind AT, is maximum allowed cold pressure, in earlyer days higher was allowed , mostly 10 psi, and prescribed even for ST tires for 75mh.

In Europe there are CP tyres especially meanth for Motorhomes( called Camper in Holland, CP ) .
Most are D load tires with 65 or 69 psi behind AT.
But max allowed pressure is 80 psi, and its sayd to be for covering peackloads , wich I explain as the overloading, often seen on rear axle of european Campers.
Then if pressure calculates above AT , you are allowed that pressure, and tou better use that to be in the clear with mother nature, though the tiremaker officially dont support the higher loadcapacity belonging to this higher pressure .

Continental groop( Continental, Semperit,Vanco,Viking) gives often on tyres for eur market, both pressures, and without AT behind sises fi 65 psi , and max inflation pressure cold of that 10 psi higher, and then higher then AT-pressure is allowed, and better most times be used to be safe to laws of nature.

End of my story is that mother nature rules above rules and prescriptions of tire and vehicle makers.
And that is what users want from their tires, a long and safe use,

[Gmdiii]

I have a Montana high country 344RL and I was wondering what tires would I replace mine with when it comes time to get new tires

[Snoking]

I have a Montana high country 344RL and I was wondering what tires would I replace mine with when it comes time to get new tires

Something equal to or better than what it came with. Appears GVWR is 14,200 and most likely has 7K GAWR. I would look at the Sailun ST235/80R16G all steel ply as a replacement. Tire pressure would be your choice, they will not need 110 pounds. 90-95 would most likely be fine.

What tires are on it now? Chris

KEY SPECIFICATIONS - 344RL FIFTH WHEEL
Shipping Weight

11472

Carrying Capacity

2728

Hitch

2265

Length

36' 4"

Height

13' 4"

Fresh Water

66

Waste Water

49

Gray Water

98

LPG

60

Tire-Size

ST235/80R16F

[CaptnJohn]

I have a Montana high country 344RL and I was wondering what tires would I replace mine with when it comes time to get new tires

Sailun S637. The same tire coming on Montana today.

[CaptnJohn]

True and the company will provide a weight/psi chart if requested.


Something equal to or better than what it came with. Appears GVWR is 14,200 and most likely has 7K GAWR. I would look at the Sailun ST235/80R16G all steel ply as a replacement. Tire pressure would be your choice, they will not need 110 pounds. 90-95 would most likely be fine.

What tires are on it now? Chris

KEY SPECIFICATIONS - 344RL FIFTH WHEEL
Shipping Weight

11472

Carrying Capacity

2728

Hitch

2265

Length

36' 4"

Height

13' 4"

Fresh Water

66

Waste Water

49

Gray Water

98

LPG

60

Tire-Size

ST235/80R16F

[CaptnJohn]

Sourdough, sorry to disagree, but ST tire are built to a lower standard. Their newer increased speed ratings are due to use of magic speed rating dust.
I have stated it many times before Semis don’t have special ST tires for trailers, all tires have the same carcass, LT’s work well on 5er with a GVWR of about 12,500#.

Semi-trailers to RVs is comparing apples to elephants. Totally different compounds. Different applications, my 5er has 4' more from the axel to tail than a trailer. Rarely do they 'curb' a tire. As a former fleet manager I disagree.

[Artizu]

Go buy 14 ply tires for your rig. I did and the trailer is much more stable and it will be much longer before the rubber breaks down to the point of failure.

The stock tires on an RV are cheap 6 ply tires and will only last 2-3 seasons.

[Jim Aitken]

Great description. Thanks

[Third Degree]

Ok, If over inflation causes problems, then what do I inflate my tires when I first start out? I am rated at 80 lbs and I have been inflating to 80 lbs when I start out. Now, I know as I travel down the highway the tires are going to heat up and the inflation is going to increase. Do I pull over every so often and release air pressure back to 80 lbs? Or, just start out at 80 lbs and everything will be fine?

[Snoking]

Ok, If over inflation causes problems, then what do I inflate my tires when I first start out? I am rated at 80 lbs and I have been inflating to 80 lbs when I start out. Now, I know as I travel down the highway the tires are going to heat up and the inflation is going to increase. Do I pull over every so often and release air pressure back to 80 lbs? Or, just start out at 80 lbs and everything will be fine?

The inflation noted on the sidewall for max load on a given tire, accounts for the fact that the pressure will go up as the tire is rolling and heats up. Cold inflation means just that, the inflation before the tire hits the road. Chris

[Sunnysidebeach]

What do you think of the new Goodyear Endurance tire.

[Snoking]

What do you think of the new Goodyear Endurance tire.

I put them on my small trailer. They are not available in a LRF for poster Gmdiii! What do you have for a trailer. I am a fan for all steel ply tires for larger trailers. XPS Rib, R250, S637 Sailun.

[Tireman9]

Ok, If over inflation causes problems, then what do I inflate my tires when I first start out? I am rated at 80 lbs and I have been inflating to 80 lbs when I start out. Now, I know as I travel down the highway the tires are going to heat up and the inflation is going to increase. Do I pull over every so often and release air pressure back to 80 lbs? Or, just start out at 80 lbs and everything will be fine?


Not sure which post you are responding too. "Overinflation" is not what you get from the normal pressure increase of running when you started out with the correct load and inflation for your RV. I have seen tires fail from running a 35 psi tire at 60 and a 60 psi tire at 150.


Only time you should be adjusting inflation is when the tires have not been run or in direct sunlight for previous 2 to 3 hours.


Trailer RV should run the pressure associated with the max load on the tire which in most cases is the inflation shown on your RV certification label.

[Tireman9]

Go buy 14 ply tires for your rig. I did and the trailer is much more stable and it will be much longer before the rubber breaks down to the point of failure.

The stock tires on an RV are cheap 6 ply tires and will only last 2-3 seasons.




You do realize that "Ply" went out in the 60's with the switch to higher strength Nylon, Polyester and finally to Steel in "Commercial grade" tires. If you read the tire sidewall you can learn the actual number of layers aka ply in your tires.
Load Range G or LR-G is the modern and correct term even though some tire companies use the "ply" designation as some customers don't understand we are really talking about the ability to retain the inflation pressure and it's the inflation pressure that supports the load not the tire itself. At least for 95% of the load. Else why Load & Inflation charts?


I have never seen a Ply vs load chart.:facepalm:

[SummitPond]

... Only time you should be adjusting inflation is when the tires have not been run or in direct sunlight for previous 2 to 3 hours. ...
You bring up a point I've been curious about. If it's really cool in the morning where you start out and ends up quite warm before the end of the travel, do you bleed or leave the pressures alone? I believe the difference in measured tire pressure between a 40 degree morning and a 70 degree morning is small (assuming no air has been added or removed between the two temperature extremes) but there will be a difference. What should one do? (I hope I'm clear in my question.)

You do realize that "Ply" went out in the 60's ... ... some tire companies use the "ply" designation ...
As for "ply", I was told at a tire store that the difference between a LR-C and a LR-D is two more plies. I opted for the higher load rating and am happy I did so; I'm just curious if I was fed a line based on your prior statement. Thank you.

[Blucaddy71]

2 Zeemax tires bought in April, less than 3000 miles on both.

18850

[Snoking]

2 Zeemax tires bought in April, less than 3000 miles on both.

18850

Your post and picture show that china bombs ST still exist. There are only two or three ST brands worth buying right now. Goodyear, Provider and Maxxis, with the Goodyear Endurance the most universally available offering.

[travelin texans]

2 Zeemax tires bought in April, less than 3000 miles on both.

18850

Seems strange that both tires have the bulges on the inside where you don't usually crawl under when doing your walk around inspection, guess maybe should start.

[CWtheMan]

2 Zeemax tires bought in April, less than 3000 miles on both.

18850


Very reminiscent of what the Uniroyal tires did on Keystone trailers in model years 2004-2006. A good indicator that overloading/under inflation on any tire in a trailer position will follow the same failure path.

The 3000 miles has nothing to do with the failure. Any mismanaged tire will fail at any time during its life span.

[Snoking]

any time (skip) any time (skip) any time (skip) any time (skip)

[sourdough]

any time (skip) any time (skip) any time (skip) any time (skip)

Point being??

[flybouy]

Your post and picture show that china bombs ST still exist. There are only two or three ST brands worth buying right now. Goodyear, Provider and Maxxis, with the Goodyear Endurance the most universally available offering.

I disagree with your list, skip, I disagree with your list, skip,I disagree with your list, skip:D

[Tireman9]

What is the DOT serial?


IMO a manufacturing issue. Have you filed complaintwith NHTSA?

[jadatis]

You do realize that "Ply" went out in the 60's with the switch to higher strength Nylon, Polyester and finally to Steel in "Commercial grade" tires. If you read the tire sidewall you can learn the actual number of layers aka ply in your tires.
Load Range G or LR-G is the modern and correct term even though some tire companies use the "ply" designation as some customers don't understand we are really talking about the ability to retain the inflation pressure and it's the inflation pressure that supports the load not the tire itself. At least for 95% of the load. Else why Load & Inflation charts?


I have never seen a Ply vs load chart.:facepalm:

Plyrating is commenly used in Europe, only when also for american market , loadranche is given.
Sometimes even both.
And ofcource it has nowadays little to do with the real mumber of plies anymore.
Here a incomplete list I made
Loadrange/ psi/ plyrating / psi
LrB/ 35 psi/ 4ply/ 36 psi exeptions to lower

LRC/ 50PSI/ 6PLY/ 55PSI has given many conversion problems in the past, so to low pressure because lrc goes from lower AT pressure.

LRD/65PSI/8PLY/ 65PSI ( 69PSI exeption but also 425 kPa= 61 psi )

LRE/ 80 PSI/ 10 PLY/ 80 PSI ( exeptions 77 and 87 psi)

So what counts is what is written behind AT in " maximum load xxxxlbs/kg AT yyy psi/ kPa ( cold)
So if you find that, forget the loadrange/plyrating, and find a pressure/ loadcapacity- list for that yyy psi and xxxx lbs/ kg.