ST to LT tires?

[elliott-maine]

I hope everyone upgrading their tires and increasing the tire pressure are checking their rims to see if it can handle the pressure. It will be stamped on the back of your rims.


Some Chinese tires are made to standards that meet or exceed what some US made tires are made to, and have excellent QC as certified by ISO.

[Tireman9]

Originally Posted by Dana Anderso

Bought my 5vr with 6 year old tires and had my first flat then. Of course I changed all tires after that and made the mistake of putting on two Japanese and two Goodyear Marathons. I blew a Japanese tire on a very very hot day.
So put the Japanese tire as the spare and put the Marathons on my car trailer, put new Goodyear Endurance tires on the 5vr. The tires have a very stiff sidewall compared to other tires like the Dunatrail and yes I actually handled the tires myself. I’ve also purchased a tpms that works like a charm so I believe I’m doing what I can to avoid problems. I fill to max cold pressure to avoid added flex in the sidewall of the tires.
That said I now drive at 60 mph always watching tire pressures and heat on the tpms. Whether this will work for you idk but it has for me and I have a better feeling moving down the road.

Yes, increased tire pressure will stiffen the sidewall but that isn't the problem that results in belt separations which lead to failed tires. It's the high Interply Shear in the belt package.
Increasing tire inflation will lower the high Interply Shear that is unique to multi-axle towables.

Unless you run low tire pressure you will not get a RLOF from sidewall flexing.


(you can learn abour RLOF HERE)

[Retired and Happy]

We often tow a cargo trailer (6x12) which will occasionally contain our golf cart along with other supplied, canopy, food, etc. Does the need for ST tires apply? The trailer came with ST, but when we had a tire go bad at a remote reststop, it was replaced with an LT, which the installer said would suffice for the loads we would be carrying. Likely he approved it because it was all he had, but we have used it spareingly for a couple years with no further problems. After reading Mark Polk's article, are we looking at a failure in our future?

[FastEagle]

Rules, regulations and industry standards are our guides for proper original equipment tire fitments and replacements for them when they wear-out, are damaged or just fail.

Vehicle manufacturers have the sole responsibility for the selection and fitment of OE tires. For RV trailers they have the option to select from any of the DOT certified highway tires in sizes starting with ST, LT, P or metric sizes. There are weight limitations for some of those tires but the regulations allow their use when they meet safe operating parameters.

Because the manufacturer’s selection is viewed as the minimum standard for the vehicle it is fitted to, tire industry standards fully support those selections with their standards. The primary standard follows the vehicle manufacturer’s statement that replacement tires MUST be of the same size as the OE tires or others approved by them. The tire industry standard supports that statement with their standard that says replacement tires must be of the same size as the OE tires or vehicle manufacturer approved options that will provide a minimum load capacity equal to what the OE tires provided.

Up to this point I’ve omitted an important word, DESIGNATED. In most tire documents from all sources that word may be in the lead sentence and thereafter just referred to as tire size. The proper nomenclature for any tire size is designated size. A designated size includes any prefix that may be part of its description. LT235/85R16, ST235/85R16 and P235/85R16 are different designated sizes and do not conform to a standardized TRA load inflation chart other than the one for their designated size. It’s primarily why almost every tire warranty package has a misapplication clause.

As owners of our trailers we are not entirely locked into tire industry standards. Most states don’t have RV trailer vehicle inspection requirements. And, most users having tire failures normally look for tires with more load capacity and durability. However, blatant disregard of tire industry standards may cause a violator a lot of grief in the time of a catastrophic failure event traced back to a misapplication.

I got this quote from NHTSA some time ago. They have a link where anyone can request an intreptutation. This is what I got when asking about the teeth in tire industry standards.

“Industry standards generally form the basis for demonstrating product safety and quality before courts, regulators, consumers and others.”

[glennwest]

I only run commercial steel carcas tires. Yes. they are LT. I have zero tire problems. They also hold air. No I will never run a ST tire on my home.

[TheKassman]

The most common cause of TT blow outs is over weight. Have you had each axel end weighed? Blowing out two tires on the same side hints at that axel end exceeding its weight limit. Also, ST tires are rated at 65mph. They are now making ST tires rated at 75mph. If your are rated at 65mph and you exceed that speed and you are over weight on the axel end you will stress the casing, heat up the tire and it will blow.

[FastEagle]

Originally Posted by glennwest

I only run commercial steel carcas tires. Yes. they are LT. I have zero tire problems. They also hold air. No I will never run a ST tire on my home.

I'm betting the real story is that trailer had OEM LT235/85R16E tires on triple 5200# - 6000# axles and you upgraded to the more durable XPS Ribs. All perfectly acceptable.

[Tireman9]

Originally Posted by Retired and Happy

We often tow a cargo trailer (6x12) which will occasionally contain our golf cart along with other supplied, canopy, food, etc. Does the need for ST tires apply? The trailer came with ST, but when we had a tire go bad at a remote reststop, it was replaced with an LT, which the installer said would suffice for the loads we would be carrying. Likely he approved it because it was all he had, but we have used it spareingly for a couple years with no further problems. After reading Mark Polk's article, are we looking at a failure in our future?

Failure in your future depends on the actual scale reading load on each tire. Possibly if you run at least 15% Reserve load and maintain cold inflation that gives you that 15% 100% of the time you might get 5 years out of the tires if you have a multi-axle trailer. If only single then you might get 6 or 7 years.

[MarcP]

Hi all, I had so many blowouts that I gave up on 15” tires and went to 16” G tires and wheels. No problems so far,3 years and counting.

[Tireman9]

Originally Posted by MarcP

Hi all, I had so many blowouts that I gave up on 15” tires and went to 16” G tires and wheels. No problems so far,3 years and counting.

Multi[ple tire failures would to me ,indicate an overload /underinflation issue.


Even with tires of greater load capacity you could still be overloading the axles as when measures it is usually fount that a majority of RV have one or more tires/axles in overload.

[glennwest]

Originally Posted by FastEagle

I'm betting the real story is that trailer had OEM LT235/85R16E tires on triple 5200# - 6000# axles and you upgraded to the more durable XPS Ribs. All perfectly acceptable.

Close but no cigar.Triple 7k axles. Came with D rated ST tires.

[Tireman9]

It would really help if a post on a tire problem included the following:
1. Full tire "Designation" not just the type or just the Load Range or that it was a 235-16
2. A picture of the vehicle certification label showing OE tire designation and GAWR

3. Actual scale weights on each tire position or at lease each individual axle weight when the RV was loaded at it's heaviest.
4. Your normal daily COLD tire inflation reading from your TPMS
5. A couple of pictures of the failed tire. close enough so no more than half the tire is in the frame. Overall are OK but many times do not provide enough detail for even a cursory examination.


Also if you are jumping in on the OP you need to provide the information listed above. Otherwise, we can't be sure which question or comment or answer is talking about which tire issue.
This thread seems to have two different issues being covered at the same time so I am not sure which tire issue is being talked about.

[FastEagle]

Originally Posted by Retired and Happy

We often tow a cargo trailer (6x12) which will occasionally contain our golf cart along with other supplied, canopy, food, etc. Does the need for ST tires apply? The trailer came with ST, but when we had a tire go bad at a remote reststop, it was replaced with an LT, which the installer said would suffice for the loads we would be carrying. Likely he approved it because it was all he had, but we have used it spareingly for a couple years with no further problems. After reading Mark Polk's article, are we looking at a failure in our future?

Replacement tires should be the same as the OE size designation, or approved options, as recommended by the vehicle or tire manufacturer.

It is recommended to match tire size designations in pairs on an axle. Do not mix radial and non-radial tires. (Cargo trailers often have bias ply ST tires).

In accordance with tire industry standards the installer did not have the option to use a replacement tire with a lower load capacity than the OE tire just because it would carry the load. The standard specifically says the replacement must be equal in load capacity to the OE tire it replaced.

Yup, I know, it’s a cargo trailer. However, the certification process is the same for all trailers.

My reference information for this post is from the USTMA.

[krsmitty]

Originally Posted by FastEagle

At that 75 PSI setting your Hercules tires are providing a little more than 25% in load capacity reserves per tire. The worst name brand you can find should have done better. You have a problem to solve before destroying some replacements. I hope you still have the failed tires so the retailer can help in solving the problem.

Sometimes when a tire has a catastrophic failure the other tire on that side will be damaged from the overload and soon fail.

When you started using the LRE tires were the valve stems checked for the higher pressure settings? Even if they put new ones in the wheels when they were changed they may have used the same type for the lower load range.

The speed rating for the Power ST2 is shown as "L"=75 MPH.

Yes, I saved the blown tires. Tire dealer is sending back to have them looked at. 62-65 is my max MPH. A little faster at times when passing.