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Old 12-11-2018, 10:01 PM   #201
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Whatís he trying to tell us about tires?

How it’s supposed to work.

Sure, there are those that set their own standards and are successful with them. You’ll read posts about all sorts of options others use. It’ll be mostly anecdotal in nature.

There isn’t much oversight on how you maintain the tires on anything you use them on, unless, you live in a state with an active vehicle inspection program.

Those of you that often read my posts probably already know I’m a real stickler for regulations and standards. That’s probably coming from my more than 10 years of having the authority to give a pilot a maintenance briefing about the aircraft he/she is going to launch in, from the flight deck of some aircraft carrier. My bottom line – with my signature – to them was, “THIS AIRCRAFT IS SAFE FOR FLIGHT. The aircraft I most often did that with was the F4 Phantom II – The F14 Tomcat – The A7 Corsair - The F/A18 Hornet.

This will be my last post in this thread. It’s going to be more explanatory. Over the years of posting about RV trailer tires I’ve stayed abreast, as best I could, with the changing regulations, standards and trailer manufacturer preferences. They intermingle, a lot, and that makes it confusing to those that have never paid much attention to tire maintenance.

How and why, are the questions most often asked? Where and when questions are close behind.

In the regulations, brands are not going to be mentioned. Tire designated sizes are standardized; brand “A” is statistically equal to brand “B”, on paper. Generally industry standards follow suit. It’s when you read brochures when brands are normally mentioned or when a brand and designated size and model are unique (one of a kind). Right now that distinction falls on the GY ST255/85R16.

OK, here we go. From the top. Federal Motor Vehicle Safety Standards. “These Federal safety standards are regulations written in terms of minimum safety performance requirements for motor vehicles or items of motor vehicle equipment. These requirements are specified in such a manner "that the public is protected against unreasonable risk of crashes occurring as a result of the design, construction, or performance of motor vehicles and is also protected against unreasonable risk of death or injury in the event crashes do occur." Here is a manufacturers guide document; https://www.nhtsa.gov/sites/nhtsa.do...e-hs811439.pdf

It’s important to always keep in mind that everything in FMVSS is strictly for dissemination and application by vehicle manufacturers. Many readers will pull - out of context - information from individual FMVSS numbers and use them in statements that are only partially correct. That’s often because, like almost all working documents such as FMVSS, the end result will contain links from other sections of the document. For instance, the FMVSS says the minimum tire requirement is for the tires to provide a load capacity equal to the vehicle’s certified GAWR. However, it doesn’t end there. Later in the document, the vehicle manufacturer is directed to use their judgment by determining what they consider an appropriate fitment is for that particular vehicle. It further directs them to then set a recommended cold inflation pressure for those tires that is also appropriate for that vehicle. It goes a step further and requires the vehicle manufacturer to certify that particular fitment for that particular vehicle and put that information on the vehicle federal certification label, in the vehicle owner’s manual and on any affixed tire/load placard. And finally it requires those tire size designations fitted during the build stage to be the same designated size depicted on the vehicle certification label at the time of first sale. Continuing on in this line of information, let’s not forget that those Original Equipment (OE) tires get registered. The listing of their serial numbers is required to be kept on file for five years. (Off topic; owners do a lot of complaining about tire failures but do little to help keep track of such failures. Every time you change tires, register the new ones.).

Just about all of the information I compile and add to my files about tire industry standards come from industry documents that are available on the WWW. Some tire manufacturers are more explanatory than others. Those that do not build Special Trailer (ST) tires will use broad terms that may not be specific enough to give a complete picture for proper tire management. Usually it’s with tire inflation. When I find them disagreeing I go to the US Tire Manufacturers Association USTMA (formally the Rubber Manufacturers Association) for their more defined answers.

The USTMA routinely publishes bulletins. Here are some that are often debated.


Some tire manufacturers have really good documents. Toyo is one of them.

All tires have the same building processes. Here is a basic chart from Maxxis.


Remember this; I bring it up in many of my posts. The vehicle manufacturer has the sole responsibility for OE tire selections. For RV trailers they can choose whatever design they deem appropriate. That selection is for that vehicle as it’s certified. Just because you have an older or newer, nearly identical model, with tires of a different basic design (size designation) does not give license to us either on your vehicle.

The vehicle manufacturer can use any highway tire with a DOT logo on it for an appropriate fitment on your trailer. Passenger, Light Truck, Special Trailer or other designated sizes, normally from the low platform of commercial tire markets.

The industry standards for replacement tires are identical for the automotive & RV Trailer industries. However, with years of corporation and collaboration with each other, the tire and automotive industries have developed listings of preapproved replacements for just about all common automotive fitments. Even down to replacing “P” with “LT” or vice versa. Those seeking replacements for their OE RV trailer tire s do not have that luxury. The standard industry and owner manual one liner for RV trailer tire replacements is; seek approval from the vehicle manufacturer. Throughout the industry the replacement tires are required to be of the same designated size as the OE tires or others recommended by the vehicle manufacturer. Never use replacement tires having less load capacity than the OE tires provided.

Like I said earlier, I’m bailing out of this thread with this post. I’ll also be throttling back on my responses to other tire related threads. I don’t use previously written (“canned”) responses and I’m just getting tired of writing the same things over and over again.

I’m also just getting tired of saying right up front “this is the way it’s supposed to be done” and getting responses with “this is the way I do it” and that way is on the other side of the ropes.

An Old Navy Aircraft Mechanic that writes about tires.
Our rig. NC mountain pull-off. US-19.
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Old 12-11-2018, 11:22 PM   #202
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Originally Posted by CWtheMan View Post
Like I said earlier, Iím bailing out of this thread with this post. Iíll also be throttling back on my responses to other tire related threads. I donít use previously written (ďcannedĒ) responses and Iím just getting tired of writing the same things over and over again.

Iím also just getting tired of saying right up front ďthis is the way itís supposed to be doneĒ and getting responses with ďthis is the way I do itĒ and that way is on the other side of the ropes.
I enjoy reading your posts. I hope that you continue to enlighten the RV community with your knowledge base on tire fitments and such.

2017 Keystone Bullet 308BHS in Saddle.
2017 RAM 2500 Laramie Mega Cab 4x4 Hemi 6.4L
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Old 12-12-2018, 01:44 PM   #203
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Originally Posted by busterbrown View Post
I enjoy reading your posts. I hope that you continue to enlighten the RV community with your knowledge base on tire fitments and such.

CW, I want to chime in with Chris. I enjoy your posts. They are informative and helpful. I think we have so many new folks that would benefit from your knowledge. I do however understand writing the same thing again and again can get tiresome. Further, as of late we have had some that want to nitpick everything said about how we are supposed to do things tire related because they don't and want to argue their point which also get tedious. Just remember that the vast majority of the folks on this forum enjoy, appreciate and learn from your posts. And, I will again say that I think it is very important for new owners to get the "real scoop". Do what you feel fits but know your time and effort writing your posts isn't wasted.

Danny & Susan wife of 50 years
2014 Ram 2500 6.4 4x4 CC
2014 Cougar High Country 319RLS
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