Me Again wrote:
CALandLIN wrote:
Those that read my posts here and on other forums under more than 6 user names may be kind enough to admit that my posts revolve around approved regulations and tire industry standards. That’s where all this information is going to come from.
Trailer tire recommended inflation pressures are different from automotive recommended inflation pressures. A quick check of your automotive tire placard will prove that, because those recommended inflation pressures are always providing a percentage of load capacity reserves.
Vehicle manufacturer recommended inflation pressures for RV trailers provide little, if any, load capacity reserves. Therefore, for may years the norm has been to insure they are inflated to the maximum amount listed for maximum load capacity. And, almost all certified RV trailer tire recommended cold inflation pressures do match the maximum inflation pressures on their sidewalls for maximum load capacity. Therein lies the first obstacle. NHTSA & the USTMA both agree that the recommended cold inflation pressures found on the vehicle certification label are the correct and minimum pressures to be used. Here is an excerpt from the USTMA PDF; “Never use inflation pressure lower than specified by the vehicle tire placard, certification label or owner’s manual. Nor should inflation pressure exceed the maximum pressure molded on the tire sidewall.”
We may all see a change in the size and load capacity of our Original Equipment tires. RVIA has made a strong recommendation for all RV trailer tires to have a minimum 10% load capacity reserve above the trailer’s certified GAWRs. Will it change the way the recommended cold inflation pressures are applied to the certification label by the vehicle manufacturer? (?).
A tire designation (ST235/80R16) may have more than one load capacity. However, all load ranges within that size designation will be compatible with the same load & inflation chart. That means that, that tire, at LRG will still provide the same load capacity as the LRE when inflated to 80 PSI.
IMO, when inflating trailer tires, any design, to the load carried is mentioned, cringe, and then, if possible add inflation that provides at least 10% in load capacity reserves.
USTMA plus sizing standards. First, does the vehicle manufacturer approve the upgrade? Will vehicle safety be compromised in any way by such an upgrade? Will the upgrade fit in the wheel well without being obstructed in any way. Is there sufficient distances between the axles - when applicable - to insure the tires do not strike each other. Will new wheels be needed to compliment the new tire size, load capacity and maybe wheel pressure constraints.
Plus sized tires must have the capability to provide a load capacity equal to or greater than what the OE tires provided. The new terminology for tire size is Size Designation, and it includes the prefix. The prefix is the primary tire design indicator. I’m going to leave that one right there. It is not clear to many people how important vehicle certification is to the industry as a whole.
Plus sizing is one of the primary purposes for standardized tire inflation charts. For instance, if you were to have ST225/75R15 LRE tires as OE on your trailer and decided to plus size them with ST235/80R16 LRE tires you would have to change wheels. Because the two sizes use completely different load inflation charts a new recommended cold inflation pressure would have to be set by the tire installer. The vehicle certification label would no longed be valid. NHTSA has foreseen that problem and allows the use of an auxiliary tire placard. The tire installer would use the auxiliary placard to display the new tire & wheel sizes and a new recommended cold inflation pressure for the plus sized tires. Notations should also be made in the vehicle owner manual. So what would be the new recommended cold inflation pressures be? The owner is, in all probability, searching for more load capacity reserves. Personally I’d insure mine had 15% above each GAWR. To match the new RVIA recommendation, 10% would be required.
To help validate your involvement with ST tires, why don't you tell the new people here about your personal experience with ST tires on your own trailers over the years and the number of failures that you have experienced?
Sure. But I don’t see that it’s very relevant to this thread.
We purchased our trailer when we started full time RVing back in 2003. The two axles have a vehicle manufacturer certified rating of 6000# ea. The Original Equipment (OE) tires were USA manufactured GY Marathons, size ST235/80R16D. (I don’t think anyone builds that tire with a LRD any more). Inflated to 65 PSI they had a load capacity equal to the axles rating. Within the first year all five had failed. By the time the 5th one failed I was deep into trailer tire researching. Found that we had a couple of wheel positions overweight and the scales became our friend. We upgraded to LRE which gave us about 18% load capacity reserves per wheel position. From then on we still had occasional failures from road hazards but the tread separations went away. Because we were high mileage users we replaced our trailer tires every 3 years.
Our trailer has about 200,000 miles on it and has had more than 30 tires. Our 2004 Tow Vehicle has, during the same time frame, had 4 complete sets and two replacements for road hazards, that‘s 28 tires counting two spare tire replacements for age. Sometimes you can miss some road hazards with the TV tires but it’s not so easy to do with the trailer tires. We have traveled in all of the lower 48 and all CDN provinces. We use steel valve stems and change them with every new set of tires. When full timing we hit the scales at least twice a year. We traveled on a lot of secondary roads which do cause the passenger side tires to drop off the pavement causing sidewall damages.
A good notation is about axles. Ours are both originals. So are the brakes, although they have new shoes when needed.
We never travel without checking our cold inflation pressures before hitting the road, even if it was just an overnight stop.
Our normal cruise control speed is about 63 MPH. We could go higher now that the new tires have a higher speed rating but for our loads the RPM at that speed is the most economical for open highway traveling.
For the past 10 years we have used a very unpopular brand but easy to find ST tire. They work well for us because we refuse to push our luck beyond 3 years usage.
It seems like all of the off shore trailer tire manufacturers are going to build the steel cased tires. Some have already got 15” steel cased ST tires at USA retail outlets.
Horror stories. Lost both passenger side tires to a road gator going west on I-15 out of Las Vegas. Catastrophic failure on I-40 at nowhere NM. Steel valve stem was gone. Something must have flew-up and knocked it off. Lost the trailing driver side tire in downtown Rochester, NY caused by hitting a protruding manhole cover. Missed it with the lead tire but it ripped the whole side out of the trailing tire. City would not pay because they had warning signs posted. Lost a lead driver side tire on a dirt road in Manitoba. Got some sort of industrial steel cable thru the sidewall. Those are just some of the dramatic ones I remember.
