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CWtheMan · 05-17-2016, 09:10 AM

Trailer tire inflation pressures are an often pondered subject in RV trailer forums. Often times getting overheated. The discussions roam from wants to needs or what is correct as opposed to what is thought to be correct.

During the trailer’s certification process NHTSA via FMVSS directs the trailer manufacturer to set the recommended cold tire inflation pressures. Those pressures are the correct pressures and are the standard from which all subsequent replacement tires will get their inflation pressures from. Industry standards do not say you cant use more than what is recommended if you have some to use and the rims have the necessary load capacity and increased pressure values to sustain higher than recommended inflation pressures. However, Industry standards will not recommend any pressures lower than what has been recommended by the vehicle manufacturer for Original Equipment (OE) tires.

Even though the same regulation (standard) is used for tire inflation on motorized vehicles and RV trailers there are differences. Motorized vehicles must have reserve load capacities via inflation. TV trailer tires do not.

The simplest way to say this is as follows: Replacement tires must be capable of providing an equal or greater load capacity (via inflation) than the OE tires. This is normally where the confusion sets in when using replacement tires of another size or design and size. What to inflate them to. The tire placard gives the answer. Remember, you must equal the load capacity of the OE tires. So you use an inflation pressure that does just that, or more, for greater reserve load capacity as long as the rims are qualified for the tire fitment.

Auxiliary tire placards are authorized for the plus sized tires. You just make one up showing the new tire size and recommended inflation pressure and place it next to the original placard. Then go and make notations in the owner’s manual.

There is no official figure for tire reserve load capacities for RV trailer tires. The RMA has always recommended 12-15% but has never been able to get the rules makers to make it official. Whenever an owner wants an extra 15% load capacity reserve it's normally going to cost more than expected because new rims will also be needed. Even if the industry starts doing it there will have to be a phase-in because of the trailer design elements that will have to be changed.

05-17-2016, 09:10 AM	#53
CWtheMan Senior Member Join Date: Feb 2010 Location: Taylors, SC Posts: 3,031	Trailer tire inflation pressures are an often pondered subject in RV trailer forums. Often times getting overheated. The discussions roam from wants to needs or what is correct as opposed to what is thought to be correct. During the trailer’s certification process NHTSA via FMVSS directs the trailer manufacturer to set the recommended cold tire inflation pressures. Those pressures are the correct pressures and are the standard from which all subsequent replacement tires will get their inflation pressures from. Industry standards do not say you cant use more than what is recommended if you have some to use and the rims have the necessary load capacity and increased pressure values to sustain higher than recommended inflation pressures. However, Industry standards will not recommend any pressures lower than what has been recommended by the vehicle manufacturer for Original Equipment (OE) tires. Even though the same regulation (standard) is used for tire inflation on motorized vehicles and RV trailers there are differences. Motorized vehicles must have reserve load capacities via inflation. TV trailer tires do not. The simplest way to say this is as follows: Replacement tires must be capable of providing an equal or greater load capacity (via inflation) than the OE tires. This is normally where the confusion sets in when using replacement tires of another size or design and size. What to inflate them to. The tire placard gives the answer. Remember, you must equal the load capacity of the OE tires. So you use an inflation pressure that does just that, or more, for greater reserve load capacity as long as the rims are qualified for the tire fitment. Auxiliary tire placards are authorized for the plus sized tires. You just make one up showing the new tire size and recommended inflation pressure and place it next to the original placard. Then go and make notations in the owner’s manual. There is no official figure for tire reserve load capacities for RV trailer tires. The RMA has always recommended 12-15% but has never been able to get the rules makers to make it official. Whenever an owner wants an extra 15% load capacity reserve it's normally going to cost more than expected because new rims will also be needed. Even if the industry starts doing it there will have to be a phase-in because of the trailer design elements that will have to be changed.