RV Trailer Tires

[CWtheMan]

I recently posted some information about bias ply tires. RVIA was the originator and Modern Tire Dealer provided an expanded version. Its been my experience that both links will have a short life span on the net so I've copied one and am presenting it here.


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Modern Tire Dealer

"As of Sept. 1, 2017, newly manufactured towable recreation vehicles (RVs) with 13-inch and larger wheels must ride on radial, not bias, tires.

A new standard requires conventional travel trailers, fifth-wheel travel trailers and folding camping trailers be outfitted with radial tires. The standard may require aftermarket tire dealers to rethink inventories of special trailer (ST) tires.

The Recreation Vehicle Industry Association (RVIA) has mandated that its member companies equip towable RVs manufactured after Sept. 1, 2017, with radial tires. Bias ply tires are not permitted on towable RVs with 13-inch or larger wheels. The standard covers virtually all new towable RV units as the RVIA represents more than 98% of total production of recreation vehicles.

The standard was developed by the National Fire Protection Association and adopted by the RVIA. Although the standard does not apply to aftermarket tire dealers, Bruce Hopkins, who is vice president of standards and education for the RVIA, believes independent tire dealers will follow his association’s lead.

“There’s no requirement for tire dealers to install replacement radial tires, but I would think they would want to. Trailers, depending on their size, have six, four or two tires. If a trailer comes in with radial tires, dealers are not going to want to replace them with bias tires.”

Mandate addresses safety concerns

Hopkins says the National Highway Traffic Safety Administration (NHTSA) identified tire failure as a key safety issue for RVs. The RVIA determined the best way to address the issues raised by NHTSA was to ban bias ply tires and provide a 10% reserve weight capacity so tires are not the weakest link in the RV’s undercarriage system.

“We take a look at the rating of the axle and then based on the rating of the axle the tires have to be 10% greater than the axle rating,” says Hopkins.

He says trailer overloading, not tire quality, leads to ST tire failures. “People have a tendency to load recreation vehicles beyond their capacity. They never think about the weight and as a result they overload the wheels and tires on one side of an RV.” The reserve weight capacity requirement also will help prevent tire failures caused by under or over inflation.

The RV market is in its eighth straight year of expansion. The industry expects to ship 472,200 units in 2017, a 9.6% increase from the number shipped in 2016. The RVIA forecasts a new peak in 2018, with production of 487,200 RV units.

Some ST tires are excluded

The new RVIA standard does not apply to tires on utility trailers and enclosed cargo trailers. But Joe Ostrowski says American Kenda Rubber Industrial Co. Ltd., which does business as Kenda USA, is seeing a strong move toward radials in the manufacture of boat trailers and enclosed trailers. He is sales manager for Kenda’s Americana Tire Division. There are two reasons behind the shift. “Number one, the pricing has gotten closer between radial and the bias. Number two, it’s a perceived improvement among consumers,” he says.

“The tire dealer is going to see fewer and fewer people wanting to see a bias replacement. If consumers look at their camper, it’s going to have radials on it, so they are going to want to stay radial.”

He feels bias tires will “never go away” for the landscaping contractor, but he expects closed trailer manufacturers will switch to radials. “I’m dealing now with people making closed trailers and more and more of them are saying we’re going ahead with radial because prices are close enough and we only have to stock one product.”

Among consumers, “there’s definitely a perceived value in the radial,” says Ostrowski. “You’re going to see more and more of that; if I were a dealer, I would stock radial.” "

[CWtheMan]

With RV trailers – mostly fivers – constantly becoming heavier, with GAWR axles at 7-8 thousand pounds, the 16” LRG steel cased tires are common OEM for OE tires.

All steel cased tires have a very dangerous side effect known as a zipper rupture. A zipper rupture is a spontaneous burst of compressed air that can occur in the sidewall/flex area of EVERY steel cord radial tire. If one fails while being serviced it can inflict serious injuries on whoever is servicing it. So, it’s best to stand fore or aft of the tire being serviced. A telltale clue to an impending failure will be small little steel wires protruding from the tire sidewall. You may find them by feeling the side wall. They can be very sharp so use protective gloves.

Here’s a picture of a Zipper Rupture from my files.

[CWtheMan]

From what I've been reading I'm going to go out on a limb and predict NHTSA will officially start requiring RV trailer builders to provide load capacity reserves for RV trailer tire fitments. Probably in the next scheduled NHTSA tire rules committee meeting.

The RVIA 10% recommendation has a side effect. The current tire industry standards for replacement tires is for them to provide a load capacity equal to or greater than what the OE tires provided at vehicle manufacturer recommended cold inflation pressures. I have never been able to find a loop hole in that standard. For awhile it looked like any tire that would qualify for providing the necessary replacement load capacity could be used. NHTSA slammed the door on that theory by making the tire designated size on the sidewall the official size indicator. If the vehicle manufacturer uses a designated size with a ST prefix, the only suitable replacement will be another ST, unless, the vehicle manufacturer will authorize something else.

Don't get confused by something a tire manufacture might say. They have zero options when it comes to OE tire fitments or their replacements. For all practical purposes, tires fitted to vehicles built under the guidance of FMVSS are totally controlled by the vehicle manufacturer. An owner can take control, but all safety actions not compiling with industry standards will become their responsibility.

Another reason I believe an official load capacity reserve for RV trailer tires is in sight is production. The off shore ST tire manufacturer's have foreseen the RVIA recommendation correctly and have quickly added new ST tire sizes and load ranges to existing tires. All major providers are now building the ST215/75R17.5 LRH tires. Just maybe, 9000# axles are in sight. Probably 450 & 550 dually trucks to haul them.

IMO, China tire plants are some of the most advanced industrial plants in the world. They move multi millions of tires per year. Most plants are relatively new with all the advanced technology found in other major plants around the globe.

[JRTJH]

What I see (from the outside looking in) is a "brother in law relationship" between the RVIA and the NHTSA. Federal regulators "conveniently looked the other way" until RVIA negotiated (or self imposed) a 10% safety margin on trailer tire fitment. Now that all the RVIA associate manufacturers are in compliance, the NHTSA "imposes a 10% requirement"....

The way I see that is the same as "me and my buddy that holds my backdated check, I get my case of beer, he gets paid, but doesn't cash the check till payday.....

Just one more "blatant example" of "government responsibility for those governed" YUP, but only if your last name is Keystone or Jayco or Uniroyal or Goodyear......

[CWtheMan]

In this post I’m going back in time to mention a subject seldom discussed any longer; RV Trailer tire degrading. By that, I mean ST tires.

Back when Carlisle was one of the “kings of the road” trailer tire providers, they had numerous documents about their tires on the net. As I recall, they coined them “Carlisle trailer tires 101”. Those documents had factors about what would limit the life expectancy of their trailer tires. The factor that I recall was the most important was tire degrading. Carlisle said that their trailer tires would degrade approximately 5% per year at 60 MPH. Let’s remember, I’m going back 20 years here. I have not seen a single trailer tire manufacturer ever mention their tire expected percentage of degrading in a long time. I’m sure the phenomenon still exists, but to what extent?

Using a hypothetical factor of 1% degrading per year, on tires providing 3420# of load capacity on 6000# axles. In three years they would be under the recommended 10% reserve load capacity recommendation. Here again, let’s remember, I’m not a tire engineer, just a researcher. So it’s just food for thought folks. However, it could be very instrumental in those tire failures in the first three years of usage. I’m pretty sure it was before the 10% reserve kicked-in.

[JRTJH]

Here is the Carlisle Tire Guide (Best Practice Recommendations) that I downloaded from the Carlisle website in 2016. While it's now 5 years old, it's the latest "guide" that I've found...

When addressing "tire age and strength relationships", in this guide, Carlisle suggest that at 3 years of age, ST tires have lost roughly 1/3 of their original strength. Using "simple math, 1/3 equals 33% and 3 years of age equals about 10% per year (assuming a linear degredation)...

So, a tire with a 2830 pound capacity at 80 PSI, in 3 years would have a maximum "calculated safe capacity" 1/3 less, or closer to 1887 pounds at 80 PSI.

[notanlines]

John, that is precisely the number that is generally thrown around on this forum and others. We sometimes have a tendency to lose track of the seriousness of what they're saying. It sure makes the 10% cushion look inappropriate.

[Javi]

Originally Posted by JRTJH

Here is the Carlisle Tire Guide (Best Practice Recommendations) that I downloaded from the Carlisle website in 2016. While it's now 5 years old, it's the latest "guide" that I've found...

When addressing "tire age and strength relationships", in this guide, Carlisle suggest that at 3 years of age, ST tires have lost roughly 1/3 of their original strength. Using "simple math, 1/3 equals 33% and 3 years of age equals about 10% per year (assuming a linear degredation)...

So, a tire with a 2830 pound capacity at 80 PSI, in 3 years would have a maximum "calculated safe capacity" 1/3 less, or closer to 1887 pounds at 80 PSI.

One of the major considerations in my choice to replace my tires every two years..

[JRTJH]

Originally Posted by notanlines

John, that is precisely the number that is generally thrown around on this forum and others. We sometimes have a tendency to lose track of the seriousness of what they're saying. It sure makes the 10% cushion look inappropriate.

Originally Posted by Javi

One of the major considerations in my choice to replace my tires every two years..

I "live on the edge" and replace my tires every 3 years. Even at that, with ST225/75R15 LRE tires @2830 each, at the end of 3 years, the new tires that could support 11300 pounds are down to around 7500 pounds. On my trailer with a 10,000 GVW and 1800 pounds on the pin, that leaves me with 8200 pounds on the tires.

So, with tires able to support 7500 pounds and 8200 pounds on them, waiting 3 years is "hanging most of my backside out there on a hope"....

Maybe, like Javi, I need to start looking at 2 years rather than 3....

Point is, how many people on this forum own a 2016-2019 trailer with OEM tires and "have no clue how their tires have degraded since they bought the trailer".... Spring is "on our doorstep" and people are starting to load up RV's for that first trip.... When it comes to the tires, looking for that MFG date is just as important as looking at the tire pressure. Especially on tires that may be "only 2/3's of their former self"......

[flybouy]

I'd be interested in knowing the number of people that check the tire air pressure, much less the "born on date". People generally do what they know. The "average" driver doesn't check their tires air pressure unless "something goes wrong" and don't replace them unless "something already has gone wrong". I don't even know how many of the "average driving public" evens know how to change a tire.

[gearhead]

So, do regular automotive tires degrade at the same rate??

[jasin1]

Originally Posted by gearhead

So, do regular automotive tires degrade at the same rate??

Hmmmmmmm. And what are the reserves on automotive tires ?

[tech740]

Originally Posted by flybouy

I'd be interested in knowing the number of people that check the tire air pressure, much less the "born on date". People generally do what they know. The "average" driver doesn't check their tires air pressure unless "something goes wrong" and don't replace them unless "something already has gone wrong". I don't even know how many of the "average driving public" evens know how to change a tire.

I can say I do both religiously. Born on date once of course so I know when to get ready to replace if I have no issues with the tire. Inflation is checked many times and monitored if the trailer moves.

[CWtheMan]

Originally Posted by JRTJH

Here is the Carlisle Tire Guide (Best Practice Recommendations) that I downloaded from the Carlisle website in 2016. While it's now 5 years old, it's the latest "guide" that I've found...

When addressing "tire age and strength relationships", in this guide, Carlisle suggest that at 3 years of age, ST tires have lost roughly 1/3 of their original strength. Using "simple math, 1/3 equals 33% and 3 years of age equals about 10% per year (assuming a linear degredation)...

So, a tire with a 2830 pound capacity at 80 PSI, in 3 years would have a maximum "calculated safe capacity" 1/3 less, or closer to 1887 pounds at 80 PSI.

I really didn't want to use that one because it's so antiquated. I know where it came from. Discount Tire used it verbatim from the older Carlisle Tire 101 documents. It was their standard ST tire information for maybe 5 years.

IMO Carlisle would no longer make those statements about their current ST tire line-up, especially their steel cased CSL series.

https://www.carlislebrandtires.com/o...-detail/csl16/

[gearhead]

Casting more doubt on the 3 year degradation, look at the warranties of Sailun and Hercules 901 HRA Strong Guard. I believe both are 6 years. Hercules will replace at no charge if less than 50% tread wear.
So what degrades? I doubt it's the butadiene, the carbon black, or the steel belts. What's left?

[CWtheMan]

Originally Posted by gearhead

Casting more doubt on the 3 year degradation, look at the warranties of Sailun and Hercules 901 HRA Strong Guard. I believe both are 6 years. Hercules will replace at no charge if less than 50% tread wear.
So what degrades? I doubt it's the butadiene, the carbon black, or the steel belts. What's left?

Compounds.
And they are confidential.

http://www.gosailun.com/Content/imag...S637T_1120.pdf

Note: A China tire industry recall was for excessive use of recycled tire rubber in their new production tires. The maximum is somewhere around 20-25%.

Another note: There is no polyester in the body construction of steel cased tires so it's a little unfair to compare them to polyester constructed tires.

[Javi]

Originally Posted by gearhead

Casting more doubt on the 3 year degradation, look at the warranties of Sailun and Hercules 901 HRA Strong Guard. I believe both are 6 years. Hercules will replace at no charge if less than 50% tread wear.
So what degrades? I doubt it's the butadiene, the carbon black, or the steel belts. What's left?

Originally Posted by CWtheMan

I really didn't want to use that one because it's so antiquated. I know where it came from. Discount Tire used it verbatim from the older Carlisle Tire 101 documents. It was their standard ST tire information for maybe 5 years.

IMO Carlisle would no longer make those statements about their current ST tire line-up, especially their steel cased CSL series.

https://www.carlislebrandtires.com/o...-detail/csl16/

So, despite the abuse that a tire is subjected to while traveling the roads of this country... hitting potholes, road debris, curbs and other unknow objects; plus the exposure to sun, rain, salt and other chemicals... that there is no degradation of weight bearing capabilities over time.

[CWtheMan]

Originally Posted by Javi

So, despite the abuse that a tire is subjected to while traveling the roads of this country... hitting potholes, road debris, curbs and other unknow objects; plus the exposure to sun, rain, salt and other chemicals... that there is no degradation of weight bearing capabilities over time.

All accountable tire damages are cumulative, the problem is measuring them. Damages from normal highway service within the steel cased tires operating parameters is probably minute. It's why the Sailun can be recapped up to three times with an 8 year warranty.

There are a lot of questions to be asked about the new breed of steel cased ST tires. The first one I'd ask is are they suitable for replacing OE polyester tires? Will the suspension of older trailers respond favorably to the stiffer, less flexible steel tires? For new trailers there is a trailer builders requirement to only fit OE tires that are appropriate for that fitment. That's a government regulation and should result in a suspension capable of supporting the design differences with the all steel tires.

[gearhead]

I don't "think" it would be the butadiene degrading. 1,3 Butadiene is one of the strongest bonds in the diene family. I operated our Butadiene unit for a couple years. It would make rubber in the distillation columns if any oxygen got in the system. We injected food grade sodium nitrite to help with that. We had to keep the acetylene level very low or it would explode. We had one of the few that didn't self destruct in that manner.
So I assume the butadiene is stable, but I know nothing of the compounds.
The recycled material would be a big unknown to me.
So are we collectively saying the steel cased tires don't degrade 5% per year?

[CWtheMan]

Designated Tire Sizes

Consumers often have a problem with tire size identification. Many of the retailers will omit a prefix from a designated size for some reason and it causes more confusion. To get a detailed description of designated sizes go to a popular tire web site like The Tire Rack or Discount Tire. Another misunderstanding is ply rating. Ply changed to ply rating when tires were not built with cotton cording. That’s well over 50 years ago, yet still being misunderstood???

The following information has been collected from the FMVSS standards the vehicle manufacturer must abide. RV trailer tires must provide a load capacity equal to or greater than the vehicle’s certified GAWRs. That’s not a consumer’s choice; it’s directed at vehicle builders. The regulations/standards for original equipment (OE) tires require the tires to be described by size designations and displayed on the vehicle certification label.

The vehicle manufacturer has the authority to set GAWRs below the axle manufacturers load certification. An example most commonly found is with 7000# axels. Before 2015 many of those axles were de-rated by the vehicle manufacturer to somewhere around 6750#. The primary reason was because of available tire load capacities within a designated size.***

The trailer manufacturer has the sole responsibility for OE tire selection by designated size. Each of the designated sizes available for selections has different design characteristics. Once selected, installed and certified they become the standard for that trailer. The only deviation allowed will be approved by the vehicle manufacturer as options. Without available options, replacement tire options would be limited to increased load capacities within a designated size.

Here is an example of the designated sizes and why interchangeability would be so difficult. Remember, load indexes numbers are official tire load capacity indicators for passenger metric and euro metric tires. Load range letters are official tire load capacity indicators for LT & ST tires.

Trailer manufacturer’s options with lookalike designated sizes.

NOTE: Passenger tires must be de-rated for service on RV trailer axles and pick-up truck axles.

225/75R15 SL/102 = 1874 --- RL/105 = 2039# --- 2039/1.1 = 1853# de-rated value.
P225/75R15 SL/102 = 1951 --- XL/105 = 2028# --- 2028/1.1 = 1843# de-rated value.
LT225/75R15 LRC = 1875# --- LRD = 2205#
ST225/75R15 LRC = 2150# --- LRD = 2540#

NOTE: There are different load index load capacity charts for P-Metric & Euro-metric tires. There are also different load inflation charts for LT & ST tires.

Whatever the vehicle manufacturer’s reasons were for OE tire selection and fitment is displayed on the vehicle certification label and is a firm commitment by them unless they have/will authorize options. Lots of consumers refer to the vehicle certification label as; “that sticker”. In actuality it’s a vehicle manufacturer provided reference to sworn documents that the vehicle meets all existing motor vehicle minimum safety standards on the date of final certification. The vehicle manufacturer is subject to very severe monetary penalties for violations with vehicle certification.

*** The ST235/80R16 LRE tires have three different load capacities, 3420#, 3500# and 3520#, all at 80 PSI. One of the FMVSS standards requires the higher two load capacity tires to default to 3420# when not properly documented. The popular tire for fitment on 7000# axles at that time was 3520#. Someone complained – justly so – and numerous recalls were issued. The easiest change was to replace the vehicle certification labels with a GAWR reduction in load capacity that would allow all tires of that size designation to be used without being a violation. The differences were deducted from the trailer’s cargo capacity.