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Old 09-02-2012, 12:02 PM   #169
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Originally Posted by w7ts View Post
This is interesting. However I think his whole logic for picking replacements and his comments about capacity are bogus. I don't care whether the computations are different or not. I am not going to replace a stock tire with one that has a lower published weight rating, no matter how they were calculated. No wonder they make a tire dealer nervous. As far as I am concerned, they should make the vehicle owner nervous as well. I think it is strange that the only times he goes up in load range is when he stays with ST tires. He total disregards the option of going from ST to LT and also increasing load range. This would make all the comments unnecessary.

Ken
In my case my Classic slide out came equipped with D rated ST Marathons. I made the assumption that increasing the load capacity of tire to E's would improve the likely hood that my tires would give me at least 5 years of service. So technically in my case, based on the manufacturer's capacity rating, I am going to a lower published weight rating. But truly in fact I still have a higher capacity than my D rated ST tires had. I'm not a tire engineer and I respect that the person doing that site is applying knowledge that you and I don't have, that technically makes those two tires almost equal in capacity in his eyes. I'll contact him and see if he can give me some level of explanation regarding his calculation and the weight ratings shown on the tire wall.

The key is that those of us experiencing less than satisfactory levels of service from our ST tires are beginning to learn that there are multiple factors adding into these failures. It has to do with road temperatures, speed, inflation and the compounds used in building the ST tires. We've attempted to deal with those issues in those things we can control. I don't under inflate my tires, I don't exceed the speed rating, I don't overload, and both sets of tires were fresh when mounted. The trailer is stored indoors so we aren't even dealing with a UV issue. The fact that I have had two sets of ST tires from different manufacturers fail with belt separation issues makes me question whether these tires carry the ability to service my sized and weight trailer as I use it over the course of 5 years.

The answer to this question will only be answered over time but so far the feedback on those who have moved to LT's has been good.

Jack
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Old 09-02-2012, 12:17 PM   #170
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Originally Posted by jcanavera View Post
The key is that those of us experiencing less than satisfactory levels of service

The answer to this question will only be answered over time but so far the feedback on those who have moved to LT's has been good.

Jack
Excellent summary. All the ranchers around here use commercial LT tires on large horse trailers because of ST tire failure history. Will see how the Michelin XPS RIB tires last.

How are your new tires working out?

73/gus
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Old 09-02-2012, 12:46 PM   #171
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We did our first trip around the first of the month. About 1,300 miles round trip up to Door County Wisconsin. No issues to report. I inflated to 77 psi prior to leaving STL. We carried no water in the holding tanks. Handling was fine although depending on the road surface, we still have issues with the cabinet drawers coming open under travel. We've had that trouble since day one when we had D rated Marathons on the Classic. Some of the Interstates are pretty poor based on dips and poor pavement. Anytime you get close to a major city, the Interstate pavement gets poor. The only saving grace is we keep the drawers lightly loaded so we haven't broken or bent any rails yet.

The only thing I did notice was that 1/2 in increased size of the tires caught me at home. I put down the front stabilizer jacks in my drive which has a small grade, prior to extending the slide out. The jacks traveled their full distance down but failed to fully rest on the concrete. I had to pull out my Lynx Leveler Blocks to reduce that distance to the ground.

Tires ran cool and I couldn't be happier.

Jack
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Old 09-02-2012, 12:52 PM   #172
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A Voice of Reason

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Originally Posted by jcanavera View Post
...
The key is that those of us experiencing less than satisfactory levels of service from our ST tires are beginning to learn that there are multiple factors adding into these failures. It has to do with road temperatures, speed, inflation and the compounds used in building the ST tires. We've attempted to deal with those issues in those things we can control. I don't under inflate my tires, I don't exceed the speed rating, I don't overload, and both sets of tires were fresh when mounted. The trailer is stored indoors so we aren't even dealing with a UV issue. The fact that I have had two sets of ST tires from different manufacturers fail with belt separation issues makes me question whether these tires carry the ability to service my sized and weight trailer as I use it over the course of 5 years.

The answer to this question will only be answered over time but so far the feedback on those who have moved to LT's has been good.

Jack
Very well stated.
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Old 09-02-2012, 03:29 PM   #173
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Tires ran cool and I couldn't be happier.

Jack
"Cool" being within 15-20 degrees of ambient?

73/gus
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Old 09-02-2012, 04:36 PM   #174
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Cool was my touch relative to the road and air temps. Tires were warm to the touch and technically cooler than my tow vehicle tires. I touch the wheels and tires every time I stop just to monitor the tire and wheel bearings and also the potential for a dragging brake. On this trip I felt that the tires were running a little cooler than the ST's used to.

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Old 09-04-2012, 09:33 AM   #175
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I emailed Barry author of the Barry's Tire Tech web site. I asked about his rating tables and specifically why I didn't see LT recommendations on the smaller wheel size (15"-14") and also to explain his calculation regarding a 16" tire having a higher load capacity than what is stamped on the tire sidewall.

The load carrying capacity is determined by the tire size (internal volume),the amount of inflation pressure, and the type of service. In essence the deflection is calculated and different service conditions need different maximum deflections.

For example, high speeds = less deflection; smooth roads = more deflection; torque and steering = less deflection; etc.

So if look at trailers as a service condition, then I have limited speeds, no torque or steering action (OK, there is cornering forces being generated, but they are small at highway speeds, and applied slowing when the forces are large), smooth roads (for the most part).

If I look at light trucks as a service condition, there would be higher speeds, torque and steering, more likely some unsmooth road surfaces, etc. Notice that all of these are directlionally towards less deflection - and therefore less load.

So the difference between those 2 service conditions is what is driving the difference in the load calculation between the 2 types of tires - and that is reflected in the published load limits.

So if an LT tire is used in an ST application, the functional load carrying capacity increases, in spite of what is imprinted on the sidewall of the tire.

But there is another issue that gets neglected when people talk about converting from ST tires to LT tires - the size changes. typically the conversion is from an ST 235/80R16 to an LT235/85R16. Notice the aspect ratio is larger - and this results in a larger load carrying capacity within a particular type of service. In this case, it's about 12% - and that is what is reflected in my chart.

It is understandable that there would be reluctance to use tires with less published load carrying capacity. I've pointed this out in the comments

Why don't I recommend using LT tires for smaller wheel sizes? Because they generally don't exist. There are very, very few LT tires in 13", 14", and 15". My chart reflects this - as well as I made the assumption that folks who use my chart won't take the time to figure out if they have enough clearance for the larger size - so I was very careful to recommend using tire sizes that minimized the change of interference.


After that exchange I attempted to drill down further on the subject of inflation tables. Earlier in my email exchange he asked if I had increased my inflation when I switch from D to E ST tires. Technically if I had relied upon the inflation tables, I should have been able to inflate my E tires to 65 lbs and get the same weight capacity as my former D tires.

I also asked him about Discount Tires claim regarding ST tires losing 1/3 of their load capacity after 3 years of life.

His response:

Inflation pressure?

I thoroughly disagree about using the load tables DIRECTLY! I think the experience during the Ford/Firestone situation a few years ago should have taught people to include some excess load carrying capacity. Some folks are even under the mistaken impression that the Michelin/Goodyear/Firestone are recommendations and are different than the Tire and Rim Association tables. Those tables are the same!

In my current job at a major tire manufacturer, I answer questions posed by consumers - and from time to time I will get a request for a load table. I NEVER give them a load table, because I know what they will do with it. I ALWAYS point to the vehicle tire placard and the owners manuals and tell them to use what is written there.

So there is at least one major tire manufacturer whose inflation recommendations do NOT include the use of the load tables.

Why the problems with ST tires?

1) Trailer manufacturers haven't done a good job of sizing tires.

2) The ST tire is pretty highly loaded.

3) ST tires aren't built by top tier manufacturers.

4) Many RV'ers overload.

So my advice is really 2 fold:

1) Weigh the trailer by wheel position.

2) Oversize the tires.

Discount Tire's statement? I do not understabnd why they would make a statement like that. It is mis-leading, but I suspect they are trying to get people's attention for tires that are frequently overlooked. Besides, ST tires are subject to the same issues other tires are, so that statement applies to Passnger Car and LT tires as well.

Why are LT owners not experiencing the same problems?

1) They are using a larger tire (more load carrying capacity relative to the service condition not what is printed on the sidewall!)

2) LT tires get much more attention by the tire manufacturers and get the better materials, design, and manufacturing technology.

And the most subtle one of all:

3) They are paying much more attention than before.


Barry


So that's the wrap from Barry. I have some issues that he never did answer to my satisfaction. One was that ST tires aren't built by major manufacturers, and my question back on that would be what about Goodyear? How do we account for that? Am I overloaded? No. But I do agree with his one statement that my tires are/were heavily loaded. He pretty much dismissed Discount Tire's statement about the weight capacity of ST tires decreasing by 1/3 after 3 years. Maybe from an engineering standpoint that might be a bad assumption, but after having two brands of ST tires fail within a 3-4 year timespan due to belt separation, something is going on there. I do agree with one of his last statements though that the good reports from those using LT tires may stem from the LT tire getting much more attention by the tire manufacturers and getting the better materials, design, and manufacturing technology.

Let's be honest, when you consider the number of vehicles that LT tires are on today, the travel trailer ST tire usage probably pales to the numbers relative to LT tire usage. Many have commented, and I at one point felt that the Goodyear rage that surfaced was skewed by the number of Goodyear tires out there in the RV industry. Just the number of tires that are OEM'ed on travel trailers by Goodyear will lead to the assumptions that Goodyear ST tires are bad.

Time I think has told us, that there is another picture and if you consider what we have collected in our shared experiences, we are seeing a picture that lays suspect that various factors are part of the soup that leads to ST tire failures. Major in that aspect is the weight of your trailer, pressures, the road conditions that you travel on (heat), and the general design of the ST tire itself, which I believe is the prime ingredient in this soup.

From my aspect I've learned a lot in this process over the past 8 years and think the RV industry needs to rethink ST tires and their performance relative to the specific trailer each manufacturer provides. One of the best improvements that a trailer manufacturer can provide is to build trailers that will allow for larger tires thus giving the trailer (even if ST tires are still provided) the ability to increase the excess capacity margin. Smaller trailers tend not to have the same % of tread separations and I think that is because the capacity margins are higher. Consider a lot of triple axle Airstreams have done pretty well with their ST's. I consider that to be the fact that those tires are carrying less load per tire, than I carry with my tandem axle Classic slide out.

Finally for those of us with the heavier trailers, it looks like the LT is our next venture and if the performance reports here stay positive, I wouldn't be surprised to see Airstream officially offer these as a build option or potentially step up and set this as their standard (at least on their heavier units).

Jack
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Old 09-04-2012, 06:32 PM   #176
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Good job, Jack. It can take a while to tease out some of the specific information folks are looking for, and few seem willing to devote the time to that. ST to LT conversions are just part of it.

A quote from CapriRacer [Barry's Tire Tech] I came across in a thread today was (in regards to pressure rise from cold during the day):

"Normal pressure buildup should be in the 10% range and anything over 15% should trigger some sort of reaction - meaning there is excessive heat being built up and the tires are headed for failure."

--------------------------

I was re-reading Tireman9's [Roger Marble's] blog, RV Tire Safety which started about 1.5 years ago and currently has 40 or so posts. Plenty there.

Here is a quote from him in re tire pressures (RV.net):

" . . the reason to run the max inflation rating on the sidewall of tires when used in multi-axle trailer application [is that] the unique cornering forces of multi-axle suspension places extraordinary and high shear forces on the internal structure of the tires during cornering.

Finite Element analysis indicates about a +25% loading when compared with the same loads but on a motorized RV with tires at the corners of the vehicle. The only way an operator can lower (but not eliminate) this overload side force is by increasing the tire inflation which will decrease the slip angle during cornering.

Doesn't make any difference if it is an ST or LT or metric tire as it is the fundamental design of trailers that is causing tire life to be so short and the failure rate to be so high. That plus the fact that the majority of trailers that have been weighed have been found to have one or more tires or axles overloaded.

Tireman9


(Interply shear)

from: RV.Net Open Roads Forum: Travel Trailers: Delima on new tires

A few more from Tireman9:

If you haven't adjusted your tire inflation based on the real corner weights for motorized [RV] units + 10% then you are ignoring meaningful and measurable benefits.

If you are not running the tire sidewall max inflation on a multi-axle towable and have confirmed you have at least 10% reserve load capacity based on real corner loads then you are ignoring meaningful and measurable benefits.

If you are not running a TPMS on all tires that are on the road you are ignoring meaningful and measurable benefits.

If you have not confirmed the accuracy of your pressure gauge against a certified gauge then you are ignoring meaningful and measurable benefits.


--------------------

(More from that blog)

If a tire looses more than 20% of its air it is considered to be "Run- Flat" by tire industry. If you have driven on a "flat" tire it is considered to have been damaged and should not be considered for future safe usage. Trying to "limp" means that you need to reduce your speed and according to the special tables in Tire & Rim Association for adjustments for speed, inflation and load your limp speed is not 30mph or 20 mph or even 10 mph, but it is limited to 2 mph. That is TWO miles per hour Maximum. Any more and you are damaging your tire beyond repair.

(So a 60-psi tire is flat at just 45-psi, for example. No "limping up to the gas station" and expecting the tire is ever again good enough to be in service).

----------------------------


And, per a link to Bridgestone Commercial Truck Tires

"In general, operating temperatures of radial truck tires can be anywhere between ambient and ambient plus 60F."

(Looks as though TPMS systems that alarm at 158F are about right).


No one wants to learn that much more about WDH or tires . . but the info to be systematic & comprehensive is available.

.
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Old 09-04-2012, 07:06 PM   #177
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You know in the old days towing a trailer was a more relaxed thing and speed limits were lower and the tow vehicles were wimpy compared to todays 400+ HP and 600+ft-lb of torque. We have to have these Monster trucks to pull 15,000 lb trailers at 80 MPH up mountains. I really don't see most trailers being pulled at less than 65 MPH. ST tires are in most cases old BIAS ply technology and if you run them at modern highway speed they will fail. I think quality of these tires is also suspect because of the off brand nature and the much looser specifications.

If you run an ST tire at 65 MPH you are at the ragged edge of the performance envelope. If you run LT or even P metric at 65 MPH you have a lot of margin there.

Perry
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Old 09-04-2012, 11:27 PM   #178
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177 posts in this thread alone and numerous other threads on same subject -- And, still debating. Simple solution: Buy the best tires, inflate to maximum pressure on sidewalls and forget about tire problems.

We run Michelin XPS Ribs (LTX M/S, also good), load range E, 225/75x16, inflated to 80 psi -- No more problems! We are now "observers", instead of "participants" in tire failure wars...
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Old 09-05-2012, 11:00 AM   #179
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No one wants to learn that much more about WDH or tires . . but the info to be systematic & comprehensive is available.

.
That's for sure.

Tire temps can increase more than 10% out west. One time we stopped in northeast Montana and morning temps were in the low 40's. Going south during the day, the temps got up to about 90˚. That increased tire temps and pressure a lot and we simply let some air out. All thing weren't being equal.

Gene
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Old 09-07-2012, 06:58 AM   #180
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Hi!

I'm Barry of Barry's Tire Tech. I dropped in because of Jack's conversation with me and wanted to see what was going on - see if I addressed all the concerns. Apparently I didn't.

Quote:
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......I have some issues that he never did answer to my satisfaction. One was that ST tires aren't built by major manufacturers, and my question back on that would be what about Goodyear? How do we account for that?.........
First, the statement I made was a generalization. Yes, Goodyear makes ST tires, but they are the only one of the top tier tire manufacturers that does. (I am hoping we don't get into a discussion about what "top tier" means.)

Interestingly, Goodyear has made these tires in China, which kind of brings into question whether or not they are using "top tier" materials, design, and machinery. Since I don't work for them, I can't say for sure. My guess is they are not - and that may explain their performance (at least partially).

Any other issues?
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Old 09-07-2012, 07:18 AM   #181
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Barry what is the max temp reading we should get on a bias ply or radial tire before things start coming apart? If the tire is of substandard quality will controlling temperatures and keeping pressure at the right levels matter?

Purely empirical data from this sight and others is telling folks to stay away from ST tires radial or bias ply.

Perry
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Old 09-07-2012, 10:20 AM   #182
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Quote:
Originally Posted by CapriRacer
Hi!

I'm Barry of Barry's Tire Tech. I dropped in because of Jack's conversation with me and wanted to see what was going on - see if I addressed all the concerns. Apparently I didn't.

First, the statement I made was a generalization. Yes, Goodyear makes ST tires, but they are the only one of the top tier tire manufacturers that does. (I am hoping we don't get into a discussion about what "top tier" means.)

Interestingly, Goodyear has made these tires in China, which kind of brings into question whether or not they are using "top tier" materials, design, and machinery. Since I don't work for them, I can't say for sure. My guess is they are not - and that may explain their performance (at least partially).

Any other issues?
Thanks Barry. I appreciate you coming over to the forum. Lots of tire questions here.

Jack
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