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Old 08-30-2016, 08:20 AM   #1
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ST to LT Tires

I am a bit confused with the debate of ST tires and LT tires on RV wheels. I have read all the dealer information, independent reviews and different forums and it appears that the manufactures and majority independent tire reviews all differ with the common thinking on the RV forums that LT tires will be a safer option. ST tires area manufactured with strong sidewalls, feature materials and construction designed to meet the higher load requirements and demands trailer towing presents. Overloaded tires, Over & under-inflated tires and Improper weight distribution are reported the main causes ST blowouts and I wonder if that is not the same for LT tires? I monitor my ST tires for wear, maintain proper nitrogen pressure and use a TMPS but is it enough from information gathered here and on other forums by experienced people who have real life experiences. I have been RVing since the seventies and have been lucky so far I guess.
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Old 08-30-2016, 09:09 AM   #2
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ST tires have extremely soft side walls. Just go to a tire dealer and check for yourself. ST tires size for size weight much less than a comparable size LT tire. ST tires are tested to a much lower standard than other tire types. That is one of the reasons they can get a higher load rating.
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Old 08-30-2016, 10:16 AM   #3
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Bombdoc has had LT tires on his rig for two years !



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Old 08-30-2016, 10:53 AM   #4
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Quote:
Originally Posted by donniedu View Post
ST tires have extremely soft side walls. Just go to a tire dealer and check for yourself. ST tires size for size weight much less than a comparable size LT tire. ST tires are tested to a much lower standard than other tire types. That is one of the reasons they can get a higher load rating.
When had my LT's mounted I compared the ST's just removed to what was being installed. Couldn't agree more, unbelievable difference. I wouldn't put an ST from any manufacturer on a little red wagon and pull it across the yard let alone put one back on my camper.
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Old 08-30-2016, 10:58 AM   #5
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3 years since this happened. LT's ever since
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Old 08-30-2016, 11:06 AM   #6
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Like TURBS said, I've been towing with LT's for a couple years. I had them balanced when installed and noticed a smoother ride instantly. I use a TPMS and Check pressure often. Haven't had an issue yet. I went with LT's due to speed rating. I wanted something that I could rely on to do 70mph when needed. I don't drive 70 very often, but coming down the mountains in TN, having a blowout due to exceeding the manufacturers recommended speed rating isn't something I worry about. 2 plus years on these LT's and I'd do it again.....so far.


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Old 08-30-2016, 11:08 AM   #7
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People do not seem to realize that it is the air pressure that carries the load not the tire construction. All the tire needs to do is to hold the air pressure. ST tires are "rated" to carry more load than an LT tire of the same size with the same inflation because:
1. The standards for ST tires were set when trailers were single axle 15' units driving at 50 mph max

2. RV industry fought hard to prevent ST tires from having to meet the update test requirements all Passenger & LT tires had to pass starting in 2002 so yes LT tires have to be better than ST tires because they are tested to a higher standard.

3. Multi-axle trailers place significantly higher shear force loads on the radial belts so the service on such trailers is tougher than on a motorized RV. With this engineering fact in mind a strong argument could be made that ST tires might need to be de-rated by 10 to 20% when placed on multi-axle trailers but again see #2 above.
This force is called "Interply Shear" you can google the term as it relates to tires to learn the science behind this fact.

To the OP, you said you reviewed many posts on ST tires. I might suggest you start reading my blog to learn what a tire engineer has to say about inflation, swapping tires, load etc.
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Old 08-30-2016, 01:45 PM   #8
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RV Trailer Tire Complexities

This topic is not as simple as it may appear. Can the trailer manufacture fit trailers with normal everyday Light Truck (LT) tires? Sure can. They can also use Passenger (P) or medium duty all position truck tires. However, Special Trailer (ST) tires were specifically designed for trailer axles. They have been around for more than 20+ years. Presently they are evolving rapidly.

Because most states don’t have laws that require tire monitoring, vehicle owners rely on retailers to provide them with tires that are safe for the normal operation of their vehicles when it comes replacement time. The automotive industry in collaboration with the Tire & Rim Association (TRA) provide listings of suitable replacement tires for all normal every-day vehicles. The tire industry has standards for plus sizing tires for your every-day vehicles. None of that applies to RV trailer tire fitments.

RV trailer tire fitments are the same in one respect, the vehicle manufacturer is solely responsible for the selection and fitment of tires to all vehicles they manufacturer. For RV trailer owners that becomes a complex problem. Few will take the time to study and understand the intricacies of the system and how it is all meshed together.

The most important factor after the fact of tire fitment is certification. This is where the vehicle manufacturer swears to the National Highway Transportation Safety Administration(NHTSA) that the tire fitments depicted on the vehicle certification label are appropriate for that vehicle as long as the recommended inflation pressures are maintained as a minimum requirement. In doing so, the trailer manufacturer has taken the tire manufacturer off the hook - so to speak - of responsibility, as long as the tire has been properly manufactured and has no defects.

Therein lies the dilemma for trailer owners and tire retailers. There are no lists for suitable replacement tires for the RV trailer. Tire designs that differ from the Original Equipment (OE) tire design are not considered appropriate unless they are on the vehicle manufacturer’s optional equipment list for that trailer. The trailer’s owner’s manual is required to have a tire safety section. That section is going to tell the trailer owner to seek recommendations from the vehicle manufacturer for replacement tires. A follow-along statement may read “ use tires of the same size and load capacity as the OE tires“. Unbeknown to most vehicle owners is the fact that ST235/80R16E is a complete tire size. The ST locks in the appropriate tire design. The suffix “E” locks in the load range of the tire.

Tire manufacturers’ retailers are going to be very reluctant to replace the ST designed tire with any other tire design. Most trailer owners wanting to change designs will do so by buying the tire and having them installed by a tire installer unaware they are going to be used as replacements for another design.

Earlier I mentioned other designs. Some are unique and others are run-of-the-mill high production tires.

Passenger tires are currently being offered as options on some hi-end Airstream trailers. Evidentially Airstream feels they may be appropriate for their uniquely designed hi-end trailers.

A unique LT is often used as OEM by some trailer manufacturer’s for service on 7000# axles. Those LTs are specifically designed for trailer service.

Truck tires designed for low bed, high cube trailers are commonly found as OEM on trailers with 8000# axles. Some of them are European designs and only have a 62 MPH speed rating. If you want to travel at interstate highway speeds you will want to avid those 62 MPH tires.

Most of the major tire manufacturers have in their tire warranty packages a section labeled “things not covered”. In that section you will find a statement about misapplication. Almost always that is going to mean your warranty will be voided if you replace OEM ST tires with any other design.

Currently there is very little excuse for not using ST tires to replace OEM ST tires. Soon all ST tires coming in from off shore manufacturers will have speed ratings on their sidewalls. Those ratings will always be higher than 65 MPH and seem to be leveling off in the 75 - 81 MPH range. All of the smaller ST tires in sizes 12” - 15” have a wide range of load capacity selections. A lot of the 15” tires now have a LRE in their desired load capacities. The 16” tires range from 3000# of load capacity to 4080# of load capacity.

There is not much name brand loyalty among trailer owners, so ST tire manufacturers are often changing names for some reason or another. Sometimes vehicle manufacturers use borderline load capacities that cause the OE tires to have a very short life span and give the brand a bad reputation. Not to worry, the name will be changed. Sometimes ST tires that are cheep, 100% cheep, not to worry, their name will change.

I guess the bottom line is tire manufacturers are going to go along with the vehicle manufacturers and not get into a long legal battle with them which they will surely lose because NHTSA stands with the Vehicle Manufacturers.
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Old 08-30-2016, 02:26 PM   #9
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Nice writeup Airdale. But you failed to look at one, and probably the most inportant aspect of all this. COST! Trailer mfgs are always looking to squeeze maximum profit from each unit built. ST tires they install probably cost them 50 to 60 dollars each. To install a more substantial LT tire would likely cost them more than a hundred dollars each. That means 200 dollars less profit per unit out the door! In 2005 my fiver came from the factory with an LT tire. They served me very well for 6 years, never a blow out, no tread seperation, no loss of pressure, nothing! Would I install a ST tire, just because they come on newer trailer of the same maker? Heck no! I may be dumb, but Im not stupid. My current LT tires are going on 6 years old and still go down the road with no issues. Given the state of ST tire manufacturing and where they are made (China) with little to no quality control, I cannot in good concencious suggest them to anyone.
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Old 08-30-2016, 03:03 PM   #10
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I think I have a pretty good grasp on the load bearing properties of air. I've been driving 300,000+ lb hovercraft on a cushion of air in the Navy for the last 14 years. The battle is keeping the air IN the tire. I can fill a basket ball to 80 psi, that doesnt mean I can put it under a 10k camper and expect it not to pop. The if the tire isn't substantial enough to hold the air in under less than perfect conditions then it's worthless.
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