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Old 11-30-2012, 12:11 PM   #29
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Iím not going to take sides in the ST vs LT thing or my tires are better than yours thing.

When a tire identified as a misapplication fails and causes an accident, it will always be at fault regardless of itís other qualifications.

Itís a consideration to be put into the mix of options when selecting replacement tires.


BlackAces


p.s. There is a way to get around the misapplication thing. Get a letter from the vehicle manufacturer authorizing you the use of LT tires as replacements for the OE tires. The LT tires will have to equal or exceed the load capacity of the OE tires. Tire manufacturers do not have that power.
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Old 11-30-2012, 12:35 PM   #30
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I’m not going to take sides in the ST vs LT thing or my tires are better than yours thing.

When a tire identified as a misapplication fails and causes an accident, it will always be at fault regardless of it’s other qualifications.

It’s a consideration to be put into the mix of options when selecting replacement tires.


BlackAces


p.s. There is a way to get around the misapplication thing. Get a letter from the vehicle manufacturer authorizing you the use of LT tires as replacements for the OE tires. The LT tires will have to equal or exceed the load capacity of the OE tires. Tire manufacturers do not have that power.

Most of my thinking about this and similar topics is spent figuring out how to avoid problems. I spend very little time figuring out to get my insurance to pay for them if they might happen. I am not the least bit concerned about this topic, because the same wheels and tires I put on my trailer are being installed by Airstream at the factory either as new options or retrofits.

If it makes you feel better to have that written statement from the factory before hand, it should not be a problem to obtain. To me it wasn't and isn't a concern.

It is my belief that the highlighted statement is your opinion rather than a fact. It is an opinion that I do not agree with and do not believe applies in this context.

Ken
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Old 11-30-2012, 01:12 PM   #31
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There is no misapplication thing.

Michelin LTX 16" tires are used as higher-end trailer (EB) standard equipment, and as an option when buying their other trailers.

I wish when people cannot make any other sense of a statement, they would not try to use some sort of legal opinion to validate it.

doug k
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Old 11-30-2012, 03:54 PM   #32
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The Airstream "Travel Trailer Owner's Manual Addendum", titled "Tire Safety Information" that came with my 2007 AS states on page 8 that "LT-The "LT" indicates the tire is for light trucks or trailers".
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Old 11-30-2012, 03:58 PM   #33
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As to the question of a safe stopping distance if you lost one tire. Assuming the remaining tire was in good shape before the loss there is no reason not to assume it would carry you to a safe stop. The thing that kills a good tire, other than road hazards, is low pressure. Low pressure creates heat and heat increases pressure to the point of explosion. Now LOW PRESSURE is not a pressure below the number printed on the tire side wall it is a pressure below the manufactures recommended pressure for the load on the tire. The time to built heat and resulting pressure is often considered to be 10 miles at road speed.

Airstream put to cheapest tires they can on at the factor just as car manufactures did for years.

The manufactures design and test tires at different loads and pressures to determine the right pressure for a given load. This design and testing is to come up with a pressure that will afford the BEST ROAD CONTACT on the tire surface. Over inflated tires reduce the contact, ware off the center of the tread and reduce the contact surface important to braking power. Under inflated tires reduce the tires resistance to prevent sidewall sway and cause the outer edges of the tire to ware prematurely. In no case did the tire manufactures consider the the life expectancy of the rivets in an Airstream as a consideration in their tire design.
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Old 11-30-2012, 04:39 PM   #34
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The Airstream "Travel Trailer Owner's Manual Addendum", titled "Tire Safety Information" that came with my 2007 AS states on page 8 that "LT-The "LT" indicates the tire is for light trucks or trailers".
What do you know about that?

I checked my manuals. I have the same book, and it says the same thing on page 8. Maybe I ought to read it. That tells me that Airstream has no problem with LT tires.

Ken
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Old 12-01-2012, 08:42 PM   #35
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The rules makers (571.110) have this description; "Light truck (LT) tire means a tire designated by its manufacturer as primarily intended for use on lightweight trucks or multipurpose passenger vehicles."

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Old 12-01-2012, 09:05 PM   #36
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The rules makers (571.110) have this description; "Light truck (LT) tire means a tire designated by its manufacturer as primarily intended for use on lightweight trucks or multipurpose passenger vehicles."

BlackAces
Note that it says primarily, not solely or only.

Ken
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Old 12-01-2012, 09:59 PM   #37
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Here is another interesting point to consider when talking about tires.

We always say a chain is only as strong as the weakest link. The build sheet from my 2013 7,300 GVW International 25FB states that is has two (2) 3,800 pound rated axles. In theory, we need a tire on each end of one axle to equal or exceed 1,900 pounds of load capacity for the tires to NOT be the weak link in the chain.

Airstream appears to utilize just the GYM ST 225/75R15D on all trailers except the EB. Thus for their convenience, they might just stock one size tire.

Since a previous poster in this thread pointed out page 8 in Airstream documentation that appears to bless the concept of LT tires (let alone Airstream installing them on the EB and offering them for sale in the show room at JC), then the Michelin LTX 235/75R15 XL tire with an actual side wall rating number of 2,183 pounds or a derated number of 1,985 pounds on other Michelin web sites (you can choose which web site to give you either weight number) exceeds the load capacity of the axle and should thus be an OK tire.

That tire could be installed on the factory rims that originally had GYM tires rated at 2,540 pounds. The lowest rated link in the chain would be the axle, not the Michelin tire that has a higher rating than the axle and four of them exceed the GVW by a wider margin (either 640 or 1,432 pounds depending on rating selected) than a single axle 22' Airstream Sport with two GYM (540 pounds). On the 30' Classic with a 10,000 pound GVW, the four stock GYM tires would have only a 160 pound margin above GVW.

Jumping to the LT 225/75R16E gives a sidewall rating of 2,680 pounds which exceeds the GYM weight rating of 2,540 pounds but also raises the trailer 0.5" which could affect the hitch angle with the TV trying to keep the trailer level. Maybe the suspension squat from reaching GVW with "stuff" would be 0.5"?

I could see the advantage of the 15" Michelin as the original wheels can be used (I was quoted $105 each for five 16" EB look alike wheels) plus the five 16" tires cost about $350 more than five 15" tires. However the 15" Michelin is 0.3" taller in elevating the trailer than the GYM 15" tire.

The search for a proper tire could easily include a tire with at least a four or five thousand pound rating that would carry the trailer if there were a tire failureÖ..

YMMV
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Old 12-01-2012, 10:25 PM   #38
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Note that it says primarily, not solely or only.

Ken
There is a very good reason for that. They are DOT certified tires for use in highway service. As such, they can be used on just about any vehicle that will allow their fitment.

LT tire designs are not as complicated as P tire designs and the ST tires are not as complicated as the LT or P designs.

The most popular LT design for use on trailers is an ďall positionĒ tire with a standard rib design. Most often referred to as a summer tire. It usually has very stiff sidewalls with very little flexing. Itís going to scrub badly in tight turns. Itís must assuredly a mileage tire with much taller treads than any ST tire. It will have a speed rating of 75 MPH or higher. It will be more durable because of extra features like added sidewall rubber to protect against curb scrubbing and in some 15Ē & 16Ē brands there will be found a third steel belt to help prevent penetrations. All will have some sort of belt stabilization such as nylon overlays or wedges. Most will be at least 50% more expensive than the ST tire. They will look better, longer, but will age out just as fast as the ST tires if not in constant use.

Thatís just little of my feedback. Others will differ.

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Old 12-01-2012, 10:32 PM   #39
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Here is another interesting point to consider when talking about tires.

We always say a chain is only as strong as the weakest link. The build sheet from my 2013 7,300 GVW International 25FB states that is has two (2) 3,800 pound rated axles. In theory, we need a tire on each end of one axle to equal or exceed 1,900 pounds of load capacity for the tires to NOT be the weak link in the chain.

Airstream appears to utilize just the GYM ST 225/75R15D on all trailers except the EB. Thus for their convenience, they might just stock one size tire.

Since a previous poster in this thread pointed out page 8 in Airstream documentation that appears to bless the concept of LT tires (let alone Airstream installing them on the EB and offering them for sale in the show room at JC), then the Michelin LTX 235/75R15 XL tire with an actual side wall rating number of 2,183 pounds or a derated number of 1,985 pounds on other Michelin web sites (you can choose which web site to give you either weight number) exceeds the load capacity of the axle and should thus be an OK tire.

That tire could be installed on the factory rims that originally had GYM tires rated at 2,540 pounds. The lowest rated link in the chain would be the axle, not the Michelin tire that has a higher rating than the axle and four of them exceed the GVW by a wider margin (either 640 or 1,432 pounds depending on rating selected) than a single axle 22' Airstream Sport with two GYM (540 pounds). On the 30' Classic with a 10,000 pound GVW, the four stock GYM tires would have only a 160 pound margin above GVW.

Jumping to the LT 225/75R16E gives a sidewall rating of 2,680 pounds which exceeds the GYM weight rating of 2,540 pounds but also raises the trailer 0.5" which could affect the hitch angle with the TV trying to keep the trailer level. Maybe the suspension squat from reaching GVW with "stuff" would be 0.5"?

I could see the advantage of the 15" Michelin as the original wheels can be used (I was quoted $105 each for five 16" EB look alike wheels) plus the five 16" tires cost about $350 more than five 15" tires. However the 15" Michelin is 0.3" taller in elevating the trailer than the GYM 15" tire.

The search for a proper tire could easily include a tire with at least a four or five thousand pound rating that would carry the trailer if there were a tire failureÖ..

YMMV
Tires MUST be fitted to provide a minimum load capacity equal to the certified GAWR found on the RV trailer's certification label.

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Old 12-01-2012, 10:38 PM   #40
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Here is another interesting point to consider when talking about tires.

We always say a chain is only as strong as the weakest link. The build sheet from my 2013 7,300 GVW International 25FB states that is has two (2) 3,800 pound rated axles. In theory, we need a tire on each end of one axle to equal or exceed 1,900 pounds of load capacity for the tires to NOT be the weak link in the chain.

Airstream appears to utilize just the GYM ST 225/75R15D on all trailers except the EB. Thus for their convenience, they might just stock one size tire.

Since a previous poster in this thread pointed out page 8 in Airstream documentation that appears to bless the concept of LT tires (let alone Airstream installing them on the EB and offering them for sale in the show room at JC), then the Michelin LTX 235/75R15 XL tire with an actual side wall rating number of 2,183 pounds or a derated number of 1,985 pounds on other Michelin web sites (you can choose which web site to give you either weight number) exceeds the load capacity of the axle and should thus be an OK tire.

That tire could be installed on the factory rims that originally had GYM tires rated at 2,540 pounds. The lowest rated link in the chain would be the axle, not the Michelin tire that has a higher rating than the axle and four of them exceed the GVW by a wider margin (either 640 or 1,432 pounds depending on rating selected) than a single axle 22' Airstream Sport with two GYM (540 pounds). On the 30' Classic with a 10,000 pound GVW, the four stock GYM tires would have only a 160 pound margin above GVW.

Jumping to the LT 225/75R16E gives a sidewall rating of 2,680 pounds which exceeds the GYM weight rating of 2,540 pounds but also raises the trailer 0.5" which could affect the hitch angle with the TV trying to keep the trailer level. Maybe the suspension squat from reaching GVW with "stuff" would be 0.5"?

I could see the advantage of the 15" Michelin as the original wheels can be used (I was quoted $105 each for five 16" EB look alike wheels) plus the five 16" tires cost about $350 more than five 15" tires. However the 15" Michelin is 0.3" taller in elevating the trailer than the GYM 15" tire.

The search for a proper tire could easily include a tire with at least a four or five thousand pound rating that would carry the trailer if there were a tire failureÖ..

YMMV
A couple of comments:

Your calculations seem correct. Remember that the weight will not be evenly distributed in any real situation, so the margin of safety is some unknown amount less on one or more tires. Also a certain amount of the trailer weight will be borne by the TV hitch. That increases the safety margin somewhat. It is a very complex situation and becomes much more so when the trailer is in motion being towed. To me, this all means that the system must be designed with more safety margin than a first look might indicate.

One other point: A half inch difference in hitch height is not a factor, because most hitch drop bars I have seen have adjustment holes that are 1 1/2 inches apart.

When I went from 15 inch to 16 inch wheels, the trailer was noticeably higher (more ground clearance). However I found that no hitch height adjustment was necessary. In fact the very slight down in the front angle of the trailer is both safer for towing and makes the rear less likely to scrape on dips. This is a concern with a 31 foot Airstream.

Ken
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Old 12-01-2012, 11:30 PM   #41
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"Would the full rated pressure enable the remaining tire to have a chance to carry the load to a safe stop better than it has less pressure?"

The answer to this question is obviously - YES.

Ken
Hi, according to the tire pressure to weight chart, I could run 35 lbs in my tires. [6300 lbs GVWR] No way that's going to happen. If I had a flat with my tires set at 35 lbs, the remaining tire would be almost on the rim.
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Old 12-02-2012, 07:29 AM   #42
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Also suggest to make sure that the wheels have the rating to carry the loads and to use high-pressure metal valve stems, if you do make a change. I converted to the Michelin LTX M/S 225/75R16E and run at 80PSI. The metal valves are much safer at those pressures.
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