Multiple Tire Blowouts

gmw photos wrote:

CALandLIN wrote:
....snip

Any highway tire can be chosen by the RV trailer manufacturer as long as it falls within the FMVSS (standards).
....snip

Cal,
My point is that LT tires are "approved" by the trailer manufacturers.

You point out that any tire within the safety standards can be chosen as OE. Which is true. They mostly choose ST, because very possibly, they are simply the least expensive to fit, and may in fact meet the needs of many consumers.

However on this board and others, forum members will state that "LT tires should not be fit to trailers. They are made for trucks. ST tires should be fit, because they are made for trailers."

This statement is contrary to what the trailer companies state. In fact a growing number of trailer companies are fitting LT tires as OE, either as standard or extra cost option.

Major point is, LT tires "CAN" be an option on a trailer, in spite of what well meaning forum posters may state.

And yes this is a much repeated forum topic, but new folks are constantly coming into the fold, looking for solid information. It makes sense to me that we repeat the dialog as often as needed.

best regards to all, gmw

I try real hard not to obfuscate.

The way you phrased “approved”, appears as an open blanket approval. It’s not. Tire selection and approval is the vehicle manufacturer’s prerogative for each application. With their selection comes the task of certification. No matter how consumers react to the validity of the federal certification label affixed to their vehicles does not lesson its binding effect on vehicle manufacturers. The tire designated size listed on that certification label sets the minimum standard for that vehicle. It trickles all the way down to replacements and the tire industry standard that says replacements must be the same size as the OE tires and able to provide a load capacity equal to or greater than what the OE tires provided. It has a caveat; deviations must be approved by the vehicle manufacturer or offered as options (SAFECAR or in the individual owner’s manual refers).

The vehicle manufacturer is directed by FMVSS (standards) to select tires appropriate for the vehicle they are fitted to and then set the recommended cold inflation pressures. Thus that inflation pressure becomes the minimum standard for the OE tires unless there are deviations in the individual vehicle owner’s manual or on a secondary tire load and inflation placard. (FMVSS 571.120 refers).
Things to put in the memory bank: Designated size has always been the official correct size nomenclature for tires. It’s becoming more important as tire manufacturers and their retailers become better trained. P225/75R15, ST225/75R15 and LT235/75R15 are all designated sizes and none of them are interchangeable.

The LT tires normally used in the current RV trailer market are actually what I call hybrid. That’s because they are marketed as Regional Service Trailer (RST) tires and have the same restriction on their sidewalls as ST tires. Up in the heavier applications, truck tires designed for service on low platform trailers are used and are normally 17.5” in diameter. However, Airstream fits some of their high end trailers with standard LT tires and offers them as options on other models. About 35-40% of all dual axle bass fishing boat trailers I observed at a recent show had OEM Passenger tires. The last RV trailer I observed with OEM passenger tires was a Dutchman Denali. It had 20” wheel/tire assemblies.

It’s very easy to be out of context when writing about tires. The reason is no single reference totally explains things from start to finish or, how they fit together. Government regulations/standards/rules are precise and there is nothing between the lines. All of us have a tendency to read-in things that are just not there. When the document says to do something, it’s directed at the responsible party – the vehicle manufacturer – and no others. In one section of the standard it says the tire must provide a load capacity not less than the load capacity of the axle system it’s fitted to. If you stop there you stopped too soon. In another standard the vehicle manufacturer is directed to fit tires that are appropriate for the vehicle they are fitted to. If they are not comfortable with the previous written minimum standard they can set it higher with their selection, which than becomes the minimum standard for the vehicle. Why? You might ask. Because they must certify their selection which came from a document of minimums.

RV trailer brochures do not provide a true reference for many things including tires. Your trailer’s brochure may list the trailer’s axles as 5200#. A true statement but inaccurate because the trailer manufacturer has the authority to recertify them to a lower capacity and certify them to 5080# which will be on the vehicle certification label.