Interply Shear Question - 15" XL vs 16" LT

[CapriRacer]

Originally Posted by OTRA15

Thanks for the input. Is there something special about Michelin tires which makes them less subject to IPS than other brands, as was suggested in these early posts?

I don't think so, because this has to do with the way tires behave when a slip angle is induced - that is, the way tires behave on a trailer.

What would make a difference would be the inflation pressure and the tire geometry (size).

Originally Posted by OTRA15

In your opinion, CapriRacer, is this last statement correct?

Let me say that I have not analyzed all the Michelin tires out there, but the ones I have done do not have unique ply angles.

Side comment: Several folks have pointed to Michelin brand tires or LT tires are being built differently than ST tires - and therefore the reason why Michelin brand or LT tires perform better than ST tires.

While Michelin brand tires are built differently than other brand tires, it has nothing to do with ply angles. What is different about the way Michelin brand tires are built probably has very little to do with their endurance qualities - since most of their major competitors have performance levels in the same vicinity.

And further, there is nothing unique about LT tires compared to ST tires. I'll bet the Goodyear Endurance tires are built exactly like their LT tires (with regard to materials and casing) and that what differences exist are things that do not matter such as tread compound, tread depth, tread pattern, etc.

If you want I can give my opinion about what the problem with ST tires was (I think we may be passed that).

Also, I can give my opinion as to what is unique about Michelin brand tires, and why it doesn't make a difference.

Fair warning: These will be somewhat technical and long and many people will find it boring - and the big one: It is not likely to change any minds.

[OTRA15]

Thanks for the thorough reply.

Peter

[crispyboy]

Originally Posted by CapriRacer

If you want I can give my opinion about what the problem with ST tires was (I think we may be passed that).

Also, I can give my opinion as to what is unique about Michelin brand tires, and why it doesn't make a difference.

Fair warning: These will be somewhat technical and long and many people will find it boring - and the big one: It is not likely to change any minds.

I would be interested in reading your opinions on these subjects.

[Action]

I would be too.

And I am pretty sure you are accurate about the last statement. In my clearly non-technical opinion, emotion has some impact.

>>>>>>>>>>>>Action

[Aironius]

My Bambi has only a single axle. So I consider it of utmost importance to run the best tire available. I use Maxxis 8008 trailer tires. They have more plies and a much higher load weight capacity than the "lesser" brands mentioned in this thread. The numbers tell the story.

[OTRA15]

FYI CapriRacer has already posted on many Michelin-related threads:

https://www.google.com/search?ei=uqs....0.2F2JEhGm7lM

CapriRacer -- FYI the blog in your signature will not open for me in Firefox on this Mac laptop.

["Please visit my website: https://barrystiretech.com/"]

FYI

[OTRA15]

PS -- The regular site opens OK FYI: http://www.barrystiretech.com/

Many interesting articles including this one on "The Effect of Inflation Pressure on Bias, Bias-Belted, and Radial Tire Performance" --

http://www.barrystiretech.com/sae800087synopsis.html

Thanks for this resource.

Peter

[BlackAces]

Even though I regularly read posts in this forum, I seldom post here any more. You have two regular members that are extremely well qualified for posting tire information. However, I am well versed in the governing body’s rules and regulations and tire industry standards. Sometimes, how to put them together, is misleading and very much misunderstood.

All DOT tires certified for normal highway services are allowed to be used for trailer/RV trailer applications. The secret lies in who has the authority for application. Original Equipment fitments for those vehicles - and all other automotive vehicles - is the sole responsibility of the vehicle manufacturer. When the vehicle manufacturer fit’s a particular tire design to a vehicle, that action is not a blanket action. The vehicle certification label displays the tire size designation, design and the recommended cold inflation pressure deemed appropriate for the fitment.

RV trailers are built to and certified to minimum standards. So the tires and their inflation pressures depicted on the vehicle certification label are the minimum allowed for that fitment on that trailer.

The Michelin thing: True, they do not build ST tires or any other trailer tires under 17.5”. However, If you own a trailer that was originally fitted with LT or P tires, they will not balk at replacing them with their brand. But, when the OE tires were ST, Michelin, like all other LT tire manufacturers, will invoke the misapplication clause in their tire warranty packages.

There is a valid federal instruction about deviations in construction/size being disallowed when not matching the vehicle manufacturers recommendations. It’s vague but can be referred to by any authority inspecting your vehicle and is probably why no one will buck it.

When an owner takes it upon themselves to alter a vehicle’s OE tire selection to a larger or smaller size, without the vehicle manufacturer’s approval, they are taking 100% responsibility for that action.

You’re not changing tire size by going to a higher load capacity with a same size and designed tire. Why? Because the tires will both use identical load inflation charts.

On that interplay sheer thing. IMO tire density and tread depth must also play a major roll. Tires with a size designation LT or ST235/85R16 LRE will have very different tread depths. ST tires have notoriously shallow tread depths. We’re told that that is a design feature to help them keep cool. Will it not also cause them to slide much easier than the ½” taller treads? If you don’t think they slide, do a sharp back-in on some concrete. You’re going to leave some rubber there (duel axle or more of course).

[tjdonahoe]

22,000 miles on 16” michelins...show no wear...rotated 3 times..doing good

[thewarden]

Originally Posted by tjdonahoe

22,000 miles on 16” michelins...show no wear...rotated 3 times..doing good

And what tire pressure are you running?

[Bill M.]

Has anybody here had or know of a tire failure that was caused by interplay shear failure? There is a lot of tread on my new Michelin's and it looks like that would allow some slack.

What good is a tire that has high interplay shear resistance if it fails from being a poor tire in general?

[switz]

This brings the discussion back to Airstream.

When one walked into the Customer Service area at the factory (2013 to 2014 time frame), at the entrance doorway was a 16" Michelin LT225/75R16/E LTX M/S2 tire and a SenDel T03-66655T wheel on display. They were being offered to anyone with a 25' or longer Airstream. That was for ANY model. One could even have them installed on a new trailer, but it came off the line on the 15" GYM tires and wheels. The trailer was taken to Customer service and switched and the 15" tires and wheels went back to the production line.

So, one can make the assumption that Airstream thinks these specific Michelins (no other brands are offered) are okay for their trailers.

The Classic owners manual had both the 15" and 16" tire info.

The falsification and hiding of fatal vehicle crash reports due to poor tire design by GoodYear for RV motorhomes sours any hope for me of their integrity in any tire designs. The fact that Airstream is installing the GYE model tires, based upon all their other parts purchase decisions on equipment in my three Airstreams, has been to get everything from the lowest bidder which includes tires.

I have run Michelin tires on all of my cars and trucks for 50 years with never a tire failure. I have had GYM ST tires fail on U-Haul trailers more times thanI can count. I even had them delaminate on the spare on a stored single rail motorcycle trailer (before I started reading this forum and found there were other choices).

I had/have Michelin tires on all three Airstreams we had or do currently own. I have the 16" as above on the 2014 31'Classic at 72/72 psi and the 15" Michelin LTX (P) 235/75R15 XL tires were on the 25FB and are on the 2015 23D at 44 psi.

Remember, once the trailer tail lights pass the exit door of the assembly line, the dealer's line of credit charged, the Certificate of Origin is printed and the trailer belongs to the dealer. The cheapest tires got the frame through the assembly process and out the door. The dealer hopes the trailer gets there with no issues. Ever notice all the spare ST tires mounted on the mobile home tugs going down the highway?

So, perhaps we are being sold a line of "whatever" that these GoodYear tires are worthy of being on anything other than perhaps a hay wagon.

[SailorSam205]

Originally Posted by Bill M.

Has anybody here had or know of a tire failure that was caused by interplay shear failure? There is a lot of tread on my new Michelin's and it looks like that would allow some slack.

What good is a tire that has high interplay shear resistance if it fails from being a poor tire in general?

From my reading, if you see a post where the tire failed with the tread coming off AND the tire carcass still held air pressure, that is likely to be an inter ply shear failure. It is my understanding of the issue, that inter ply shear (twisting of the tire) breaks the bond of the tread from the tire carcass. This may start as a small section that can be seen as a bubble under the tread. Then rolling the tire expands the failed area until in all comes apart.

FWIW, I've seen plenty of these posts. I suspect it is also possible for the tread to separate from the carcass and in the process of self destructing, punctures the tire carcass resulting in tire deflation.

[Tireman9]

Originally Posted by SailorSam205

From my reading, if you see a post where the tire failed with the tread coming off AND the tire carcass still held air pressure, that is likely to be an inter-ply shear failure. It is my understanding of the issue, that inter-ply shear (twisting of the tire) breaks the bond of the tread from the tire carcass. This may start as a small section that can be seen as a bubble under the tread. Then rolling the tire expands the failed area until in all comes apart.

FWIW, I've seen plenty of these posts. I suspect it is also possible for the tread to separate from the carcass and in the process of self-destructing, punctures the tire carcass resulting in tire deflation.

Sorry for joining this thread late. It didn't pop up as something for me to look at in the last couple of days. Been laying vinyl plank floor in the bathroom for "She who must be obeyed"


Ok to the questions of IPS (nice acronym BTW)


All belted tires exhibit this force. It is a function of having belts under the tread that are at a high angle relative to the low angle body ply. Here low angle is about zero with the body ply running radially from bead to bead. Belts are generally in the range of 60 to 70 degrees relative to the body ply. The two belts run in opposite direction. (note different tire companies use a different reference for the "radial" Some call that 90 degrees and they say their belts run in the 20 to 30-degree range but the result is the same.


Do tires ever fail due to IPS. Yes, What is it that you think causes belt separations off each other or off the body? ( Air loss or not is not a controlling factor as air loss can occur because the belts have separated from the body which allows tearing of the rubber between the body ply cords)


In THIS post the two PRIMARY reasons for tires to fail are covered. We are not talking about air leak here.



It is the air pressure that supports the load, not the tire construction (ya the tire does support some of the load but maybe only 5% at best so we are discounting that)


In general, a stiffer tire can generate higher cornering force than a tire with low inflation. Cornering force is not just from the contact area. This is well known in the racing community as our tires generally run higher pressure than we would run on the street. This I know from first-hand experience running and winning numerous road course events in my Camaro. (6-time winner of the 24-hour race at Nelson Ledges, Lap records at 6 different tracks including Daytona, Mid-Ohio, Watkins Glen and others) I ran DOT street tires" as required in my class and most of the time ran 34 to 36 psi cold vs an estimated 20 to 22 psi which is what I would have needed to simply support the actual load.


capriRacer's posts are correct. So that makes the two tire engineers on your forum in agreement.


We don't need to get into the sales (price) and marketing decisions of RV companies. We as RV owners are trying to get the best durability and overall performance from the tires we run on our RVs. CapriRacer and I do our best to provide the most technically accurate information and responses to your questions we can.


Tire durability (not coming apart) is out number one goal. You can choose to follow our recommendations or no. All I ask is that you not complain if or when you have a tire failure that has the root cause of the failure traced to a failure to follow our recommendations.

[jcanavera]

And to add to the real world side of this conversation, the early pioneers with the Michelin LT tires are probably 8+ years into this "experiment". Many of us ventured into this with a little trepidation, but when you look over the years, we have not seen any mass failures, or back peddling for those who made the LT Michelin jump. I'm in season 6 of my Michelin's and in my case I'm coming from the ST world with my heavy 30' slide out, and having ST failures on ST tires (the Marathons and then the E rated Maxxis ST's), all with belt separation issues and all running max sidewall pressures. The Marathons failed at the last trip of season 3 of use, and the Maxxis failed after one trip at the beginning of season 4.

While many comment regarding how well their ST tires have performed, I really feel that they underperform on my specific trailer based on weight and the hot summer conditions we operate in.

It's really not a controversial choice any more. The Michelin LT will do the job and in many cases will provide superior performance for some users. I did the math and even though the Michelin's cost me more, that when you consider that in my experience replacing ST tires just before the 4th season of use, costs me more in the long run than replacing the Michelin LT at the end of year six.

FYI I do run my Michelin's at 80 psi cold. I've had not structural issues or rivets popping on my soon to be 15 year old Classic slide out.

Jack

[Tireman9]

Originally Posted by jcanavera

And to add to the real world side of this conversation, the early pioneers with the Michelin LT tires are probably 8+ years into this "experiment". Many of us ventured into this with a little trepidation, but when you look over the years, we have not seen any mass failures, or back peddling for those who made the LT Michelin jump. I'm in season 6 of my Michelin's and in my case I'm coming from the ST world with my heavy 30' slide out, and having ST failures on ST tires (the Marathons and then the E rated Maxxis ST's), all with belt separation issues and all running max sidewall pressures. The Marathons failed at the last trip of season 3 of use, and the Maxxis failed after one trip at the beginning of season 4.

While many comment regarding how well their ST tires have performed, I really feel that they underperform on my specific trailer based on weight and the hot summer conditions we operate in.

It's really not a controversial choice any more. The Michelin LT will do the job and in many cases will provide superior performance for some users. I did the math and even though the Michelin's cost me more, that when you consider that in my experience replacing ST tires just before the 4th season of use, costs me more in the long run than replacing the Michelin LT at the end of year six.

FYI I do run my Michelin's at 80 psi cold. I've had not structural issues or rivets popping on my soon to be 15 year old Classic slide out.

Jack

jack can you provide info on


OE ST tire size, Load Range and tire placard inflation and the cold inflation you ran.


Current LT Size, LR. I see you run 80 psi.
By any chance do you have actual scale weights for each axle or if not that for both axles together?


Do you run a TPMS?

[jcanavera]

Tireman9,my OE tires on my slide out were 225 x 75 R15 load rated D Marathons. On my last camping trip of the 3rd season of use I lost pressure suddenly while backing into my drive. Found a patch of tread missing and the belt was torn. Tires were run at 65 PSI. Airstream's Vin sticker on the trailer showed 9,100 lbs. I can carry up to 60 gallons of fresh water and do that once a year. Rest of the time that tank may have a couple of gallons of water in it. With full camping load, food, fridge, and clothing and the stuff in the back underbid storage, I'm adding an additional of 500 lbs to the empty weight of the trailer. I feel that with that full water tank, I'm probably around that 9,100 lb gross.

After that failure I swapped the entire set of tires to Maxxis ST E rated tires. Those were rated a little higher in weight capacity at 80 psi, which is what I ran. Size 225 x 75 R15. First trip of season 4 I again came home and once backing the trailer into the drive I went to put in the wheel chocks and found that both front tires showed signs of belt slippage with signs of air between the tread and the belt. The tires were at that point were physically taller. I have a picture here on the forum of the tires standing next to the rear axle tires. Quite remarkable in that again I caught a failure prior to having it happen on the road.

Bought a complete set of Michelin LTX MS2 tires about 6 years ago. Tire sized 225 x 75 R16 E rated. Have also run those at 80 psi cold.

I bought these from Discount Tire Direct and they used to have a post about ST tires on their web site. I know that post stated that for every year of a ST tire's life, the rated load capacity was reduced by a certain %. Bottom line it gave me the distinct impression was that my ST tires were failing due to the fact that by the end of year 3 of use, the reduced load rating of the aging tires were possibly being exceed by the weight of my heavy Classic. It made sense in my eyes and quite honestly I've always felt since reading that post that 3 years was probably the limit for ST tires on my specific trailer. I decided that a swap of tires ST every 3 years was more expensive than getting 6 years out of a set of Michelins. My plan is to replace the Michelin's before our first outing next spring.

FYI I don't have a TPMS but I am quite anal on making sure tires are at max sidewall pressures when cold prior to leaving on a trip. My trailer is stored inside and the tires sit on a covered concrete surface. So we aren't dealing with UV deterioration or leaching of the tire into a bare concrete surface. I don't exceed 65 mph and most cases I drive a stray 60 mph.

Whether Discount Tire's theory of decreasing load capacity of ST tires over time holds any water, but its the closest thing I can come up with that makes some sense to explain my failure experience. At the time my trailer was the heaviest trailer that Airstrem built on tandem axles which pretty much meant that my ST's were caring more load per tire than any other Airstream I was aware of, except the larger single axle trailer which may have carried slightly more weight per wheel.

Jack

[CapriRacer]

Jack,

I know you addressed this to Roger, but I hope you don't mind if I comment on some things I found interesting in your post.

Originally Posted by jcanavera

...… After that failure I swapped the entire set of tires to Maxxis ST E rated tires. Those were rated a little higher in weight capacity at 80 psi, which is what I ran. Size 225 x 75 R15. First trip of season 4 I again came home and once backing the trailer into the drive I went to put in the wheel chocks and found that both front tires showed signs of belt slippage with signs of air between the tread and the belt. The tires were at that point were physically taller. I have a picture here on the forum of the tires standing next to the rear axle tires. Quite remarkable in that again I caught a failure prior to having it happen on the road. ……

I suspect the reason the tires were physically larger was that the Maxxis's had cap plies and that's what prevented the tread detachment that you experienced earlier with the Goodyear Marathons. That is, both tires suffered belt leaving belt separations, but the cap plies acted like a bandage. It may also be the reason why you were at season 4, where previously you were at season 3.

Cap plies reduce the amount of centrifugal movement - and therefore that amount of stress the belt edges experience.

However, cap plies, in and of themselves, are not sufficient to prevent belt leaving belt separations.

Originally Posted by jcanavera

...… Bought a complete set of Michelin LTX MS2 tires about 6 years ago. Tire sized 225 x 75 R16 E rated. Have also run those at 80 psi cold. ….

From a tire engineering perspective, this change was also a load carrying capacity increase, just like the change from LR D to LR E you did the step before. This is on top of the change from ST to LT and the change from Maxxis to Michelin. Statisticians would say that those 3 things are "confounded" - meaning you can't figure out which change is significant given the data in front of you.

Originally Posted by jcanavera

...… I bought these from Discount Tire Direct and they used to have a post about ST tires on their web site. I know that post stated that for every year of a ST tire's life, the rated load capacity was reduced by a certain %. ...…

I really dislike the way they did that statement. I think they were very awkwardly trying to explain that the number of cycles loaded (revolutions) plays a role in a tire's life and that one should not expect a tire to last forever.

However, they seemed to imply that ST tires are different than other types of tire in this regard. They are NOT! ALL tires have this property. It's a part of the way this works - a "Laws of Physics" kind of thing. In engineering terms, this is called "Fatigue".

[Tireman9]

Originally Posted by CapriRacer

Jack,
I know you addressed this to Roger, but I hope you don't mind if I comment on some things I found interesting in your post.
I suspect the reason the tires were physically larger was that the Maxxis's had cap plies and that's what prevented the tread detachment that you experienced earlier with the Goodyear Marathons. That is, both tires suffered belt leaving belt separations, but the cap plies acted like a bandage. It may also be the reason why you were at season 4, where previously you were at season 3.
Cap plies reduce the amount of centrifugal movement - and therefore that amount of stress the belt edges experience.
However, cap plies, in and of themselves, are not sufficient to prevent belt leaving belt separations.
From a tire engineering perspective, this change was also a load carrying capacity increase, just like the change from LR D to LR E you did the step before. This is on top of the change from ST to LT and the change from Maxxis to Michelin. Statisticians would say that those 3 things are "confounded" - meaning you can't figure out which change is significant given the data in front of you.
I really dislike the way they did that statement. I think they were very awkwardly trying to explain that the number of cycles loaded (revolutions) plays a role in a tire's life and that one should not expect a tire to last forever.
However, they seemed to imply that ST tires are different than other types of tire in this regard. They are NOT! ALL tires have this property. It's a part of the way this works - a "Laws of Physics" kind of thing. In engineering terms, this is called "Fatigue".

^ Yup. What he said.


The "Interply Shear" is the technical term for the forces in radial tires that can eventually result in ANY tire failing. It does take time for these forces to initiate microscopic cracks which over more time grow. The cracks NEVER get smaller or "repair" themselves. IMO Discount was just trying to tell people you will get shorter life with ST tires when in reality you will get shorter life when any tire is placed on a multi-axle trailer than the same tire would deliver if on a motorized vehicle (P/U or Motorhome).


In my blog I cover, with video, how the average AS owner can "catch" and "prevent" having a tire failure on the road. It's called "Free Spin" inspection. Now this inspection is intended to let the owner see the belt "slip" or "separation" or 'detachment" before it becomes big enough to result in the tire coming apart. I am currently suggesting the inspection be done annually or every 2,000 miles which ever comes first.


This inspection will not address an air leak while running down the road. TPMS can do that.

I also have a blog post of a "Blowout" July 22, 2012 on an AS that happened 50 miles after the air pressure was checked. The report shows, with photgraphic evidence tha failure was the result of an air leak. IMO if the owner had been running a TPMS he would have been warned befroe the tire failure and before there was damage to his AS and before he had to sit on the side of an Interstate for a couple hours.

[SailorSam205]

Originally Posted by Tireman9

It's called "Free Spin" inspection. Now this inspection is intended to let the owner see the belt "slip" or "separation" or 'detachment" before it becomes big enough to result in the tire coming apart. I am currently suggesting the inspection be done annually or every 2,000 miles which ever comes first.

Roger,
I understand the inspection, but did you really mean every 2,000 miles? For me, that would have me jacking up my trailer multiple times per trip. I've got a trip planned to the Grand Canyon and Albuquerque that is about 5k miles...