Disaster Averted

[blkmagikca]

Two days (Monday) ago I drove down to Jackson Center to get some servicing done. The trip down was long (725 miles in one day) but uneventful. On Tuesday, my trailer was brought into the service bay and the items I wanted done were started. It was then that Bob, one of the techs noticed that one of my tires was bad. It turned out that the tire was defective and that the tread had separated from the belt. After the tire was changed, I was able to pick the break open and gaze down the full width to the shiny steel belting. I was fortunate that the defective tire did not blow out on me. Kudos to the guys at JC.

[Protagonist]

Tread wear seems indicative of persistently low pressure. May want to keep an eye on that in the future for all of your tires.

Not saying the tire wasn't defective, but low pressure may have been a contributing factor.

[Silver Hawk]

From the tread, that looks like one worn out tire - what do the rest look like?

[blkmagikca]

The tires are not quite 3 years old - they were newly purchased when I took delivery of the trailer. Last fall one of the tires (street side front) was badly worn and JC determined that it was an alignment problem. The 3 remaining tires were fine. This tire was on the curb side front - the other 2 of the original tires are fine - no abnormal wear pattern.

All the tires are load range E. For the first year I was inflating them at 80 psi, but last year JC recommended 65 psi. I have a TPMS system active and the tires have never been run under- or over-inflated from what they were set at. Bob at JC said that it was a defective tire. Obviously if the belt came loose, the wear pattern would be something like what I had in this case.

Ever since I had a blowout on my LY motor home on the way to the International at Bozeman MT, I have meticulously checked tires, tire pressure, and (even more so) the date codes of all tires I have on all my vehicles.

In this instance, I was the beneficiary of Lady Luck.

[handn]

Originally Posted by Silver Hawk

From the tread, that looks like one worn out tire - what do the rest look like?

As a victim of serial ST tire failures, I am asking the same question. My experience is that once one blows the others are not far behind.
Do your AS a favor and upgrade to LT tires. If nothing else you will notice the oxcart ride of your trailer is gone.

[blkmagikca]

Originally Posted by handn

As a victim of serial ST tire failures, I am asking the same question. My experience is that once one blows the others are not far behind.
Do your AS a favor and upgrade to LT tires. If nothing else you will notice the oxcart ride of your trailer is gone.

Please explain to me what the differences are between ST and LT tires, assuming both have the same size and load rating. Are their casings made differently?

I should mention that the tires had been purchased for me by the PO at the time I negotiated the purchase of the trailer. The tires on both the truck and trailer were outdated and I refused to travel the 1,000 miles home with them. The truck tires he got for me were Firestone - load range E. They were worn out this spring and I put a new set of tires on the truck.

My intention now is to replace the remaining two + spare of the tires I got at the time I took delivery of the trailer. Better safe than sorry!

[DKB_SATX]

Originally Posted by blkmagikca

Please explain to me what the differences are between ST and LT tires, assuming both have the same size and load rating. Are their casings made differently?

I should mention that the tires had been purchased for me by the PO at the time I negotiated the purchase of the trailer. The tires on both the truck and trailer were outdated and I refused to travel the 1,000 miles home with them. The truck tires he got for me were Firestone - load range E. They were worn out this spring and I put a new set of tires on the truck.

My intention now is to replace the remaining two + spare of the tires I got at the time I took delivery of the trailer. Better safe than sorry!

One of the tire experts may chime in with info on the construction of the tires themselves, but one key difference I see is that LT tires are good enough that tire-company lawyers can sleep at night when they're installed on passenger-carrying vehicles, and ST tires may not be.

[Protagonist]

Originally Posted by DKB_SATX

One of the tire experts may chime in with info on the construction of the tires themselves, but one key difference I see is that LT tires are good enough that tire-company lawyers can sleep at night when they're installed on passenger-carrying vehicles, and ST tires may not be.

It's my understanding that ST tires are built to different specifications, due to having to meet different Federal Motor Vehicle safety Standards (FMVSS). Passenger car tires (including light truck tires) have to meet FMVSS 109 and 110. Trailer tires have to meet FMVSS 119 and 120 instead.

[DKB_SATX]

Originally Posted by Protagonist

It's my understanding that ST tires are built to different specifications, due to having to meet different Federal Motor Vehicle safety Standards (FMVSS). Passenger car tires (including light truck tires) have to meet FMVSS 109 and 110. Trailer tires have to meet FMVSS 119 and 120 instead.

Browsing the 4 documents, it appears that the distinction between 109-110 and 119-120 is whether the GVWR of the vehicle is above or below 10k lb. Motor homes and RV trailers are specifically mentioned in each, and the distinction is the range of the GVWR, if the articles' own statements of application are to be believed.

ST tires are specifically called out in 119's statement of application, but so are "(a) New pneumatic tires for use on motor vehicles with a GVWR of more than 4,536 kilograms (10,000 pounds) manufactured after 1948;
(b) New pneumatic light truck tires with a tread depth of 18/32 inch or greater, for use on motor vehicles with a GVWR of 4,536 kilograms (10,000 pounds) or less manufactured after 1948;" which would seem to cover LT tires.

In the application statement for 109, it says "This standard applies to new pneumatic radial tires for use on passenger cars manufactured before 1975, new pneumatic bias ply tires, T-type spare tires, ST, FI, and 8–12 rim diameter and below tires for use on passenger cars manufactured after 1948. However, it does not apply to any tire that has been so altered so as to render impossible its use, or its repair for use, as motor vehicle equipment." so this also refers to ST tires, presumably for applications under 10k lb GVWR... or are there 2 types of ST designation?

Apparently there's another standard for radial passenger tires for cars manufactured during and after 1975 (I didn't search for it.)

[blkmagikca]

BTW, the tire was branded "Westlake"; the country of manufacture was China and it was date coded 1211. So 2 of the 4 tires installed 2 years ago have bitten the dust. Even though the remaining two look OK, I'll be changing them real soon.

[CapriRacer]

Originally Posted by blkmagikca

Please explain to me what the differences are between ST and LT tires, assuming both have the same size and load rating. Are their casings made differently? ........

You will get quite a few conflicting answers to this - but here is my 2 cents.

No, there is no difference at all in the casing between ST and LT tires - once you factor in the differences between brands.

Put another way, ST tires and LT tires should be built the same. There will be difference in tread depth, tread width, tread compound, but the casing should be the same.

- HOWEVER -

There are differences between brands.

- AND -

There can even be differences within a brand. Things such as differences in which plants, and/or which piece of equipment is used to build the tires can affect the casing construction.

I think all of those things factor into the ST vs LT issue.

As perspective: I hope everyone understands that the Firestone recall some time back completely changed the landscape surrounding tires - that separations in tires were unacceptable. The problem was the technology needed to do that.

The first group of tires to be addressed were passenger car tires. These type of tires are such a HUGE percent of the population of tires that not only did it make complete sense to do these first, but it was this type of tire that was involved in the whole Firestone situation. There was some knowledge about high speed tires that rarely fail that could quickly be incorporated. Even at that, it took a while before this could be completely adopted, because it required some changes in building equipment.

LT tires were next- but here, not only was there much less knowledge to draw upon, but the pressure to change was considerably less. I am of the opinion that the tire industry is just now tying up the loose ends on LT tires and have turned the attention to other types of tires - ST tires being among them.

Not only are ST tires produced by only a few tire manufacturers - and many of those do not have good feedback systems - but there is a similar lack of knowledge about what would work to address some of the issues being brought forward.

To further complicate things, many of the foreign tire manufacturers are still coming to grips with the way regulations work in the US. There is a major misconception that if a product meets the regulations, it is acceptable for use - and nothing could be further from the truth.

Meeting the regulations only means that the product is legal for sale - NOT that it will perform adequately NOR that US consumers will find the product acceptable.

The problem is that the competitive pressure the market usually applies to products isn't very strong in ST tires. It will take quite a long time before this completely sorts itself out.

So you will find many complaints about ST tires - and many complements about the performance of LT tires in their place. But there are many, many factors involved, so I don't think the difference in performance is solely the difference between the letters on the sidewall.

[blkmagikca]

Thank you CapriRacer.

I had a chance to discuss this yesterday with an old friend who at one time was managing a fleet truck repair facility for a supermarket chain; he's a mechanic as well. His explanation went along the following lines:

He said the LT tire by its nature "squirms" (for the lack of a better word) - i.e., there is constantly some sideways pressure as it is used for steering. The ST tire, on the other hand, was load carrying and following, and therefore the "squirm" factor was not as important.

My own observation is that the tread of the LT tire is both deeper and has "lugs" on the side to stabilize steering, whereas the ST tire has a shallower tread and its design is more for straight line rolling.

Having said all this, I am not an engineer nor am I knowledgeable in design aspects of tires - mine is just a consumer's observation. My concern, however, is to ensure I am safe on the road. The trailer's sole contact with the pavement is through those 4 little patches of rubber as my tires roll. My objective is to avoid costly failures and repairs; to do this I have my trailer serviced at JC twice each year, once when I head south for the winter and again when I head north for the summer. My trailer gets towed about 12,000 miles a year.

[CapriRacer]

Originally Posted by blkmagikca

Thank you CapriRacer....

You are quite welcome.

Originally Posted by blkmagikca

.......I had a chance to discuss this yesterday with an old friend who at one time was managing a fleet truck repair facility for a supermarket chain; he's a mechanic as well. His explanation went along the following lines:

He said the LT tire by its nature "squirms" (for the lack of a better word) - i.e., there is constantly some sideways pressure as it is used for steering. The ST tire, on the other hand, was load carrying and following, and therefore the "squirm" factor was not as important.

Well, all tires squirm - which the term commonly associated with the movement the tread surface makes as it goes into and comes out of the footprint.

But I think your friend is wrong about the steering forces being constantly sideways. I don't think there is any difference for free rolling tires. You could argue that driven tires are under a constant torque, and that is a difference in operation such that they would result in different load ratings.

[QUOTE=blkmagikca;1335335].......My own observation is that the tread of the LT tire is both deeper and has "lugs" on the side to stabilize steering, whereas the ST tire has a shallower tread and its design is more for straight line rolling.....[/quote[

I think this is more a case of tuning the tire for the application. BOTH tires could be identical, but an ST tire used in the LT application is well suited to the task as an LT tire used in an ST application.

But I think that sort of difference is not really a big point. The casing is the same (in my opinion).

Originally Posted by blkmagikca

.......Having said all this, I am not an engineer nor am I knowledgeable in design aspects of tires - mine is just a consumer's observation. My concern, however, is to ensure I am safe on the road. The trailer's sole contact with the pavement is through those 4 little patches of rubber as my tires roll. My objective is to avoid costly failures and repairs; to do this I have my trailer serviced at JC twice each year, once when I head south for the winter and again when I head north for the summer. My trailer gets towed about 12,000 miles a year.

I think there is some logic to using tires from 1st tier manufacturers - and most ST tires are made by 3rd tier manufacturers. I also think that even 1st tier manufacturers produce ST tires on 3rd tier equipment or use 3rd tier processes.

Overall there is logic to making a switch to LT tires.

- BUT -

It isn't like there is a simple substitution. There is very little size commonality, which makes the switch a bit problematic.

- PLUS -

There are issues with having a bog enough tire to carry the load. Passenger car manufacturers used to use the smallest tire they could. Over the years they have gone larger. If you do the math, your car will have tires that are about 3 sizes larger than the calculation. I think this lesson needs to be applied to ALL vehicles - and trailers seem to be way, way behind the curve on this.