[Javi]

Originally Posted by CWtheMan

For the last couple of weeks I’ve been updating my vast library of tire references. In doing so I’ve determined that in many instances, I’ve been as negligent in writing about tire sizes, as many of the writers of official documents have been.

All of the references that I’ve updated have been more concise with tire descriptions. In the past, tire size was just a couple of words (tire size) put together to inform the reader what a topic might be about. The industry using that short two word phrase was being lackadaisical in their presentation. So was I. Tire size, in itself, does not actually describe a tire’s intended use. Its intended use is only evident when a vehicle manufacturer selects it for use on a specific vehicle. That is done in the vehicle’s final certification process. The governing body document, for RV trailer tires, is the Federal Motor Vehicle Safety Standards (FMVSS). So, here’s a list of designated tire sizes you may find on your trailer’s axles.

ST225/75R15
LT225/75R15
P225/75R15
215/75R17.5

The significance of the prefix in a tire’s designated size is to distinguish its basic design from other designs

The Rubber Manufactures Association (RMA) has recently renamed itself, US Tire manufacturers Association (USTMA). This is a quote from their current document of industry standards;

(“Replacement tires should be the same as the OE size designation, or approved options, as recommended by the vehicle or tire manufacturer. Never choose a replacement tire of a smaller size or with less load-carrying capacity than the OE tire size at the specified vehicle tire placard pressure.”)

You see, they have done it again. At least they set the precedent (size designation) early in the paragraph so they could shorten it later.

So, then.... it would be acceptable to replace an ST235/80R/16 with an LT235/85R/16 because SIZE does matter and the ST vs LT debate is dead... ? ? ?