Since this thread is a platform for technical stuff about the tires used on RV trailers, I’m going to use it to see if I can explain some of the underlying myths. And, just maybe something about regulations that muddy the waters surrounding the myths.
The paragraph quoted below can be found in your Keystone owner’s manual. Why? Because it’s mandated to be there by the DOT. It’s a NHTSA safety standard. It supports tire fitment and vehicle certification regulations that empower vehicle manufacturers to set recommended (correct) tire pressures for the tires on your trailer. The recommended tire pressures insure your trailer’s tires are providing enough load capacity to satisfy the needs of the trailer’s certified GAWR.
“To maintain tire safety, purchase new tires that are the same size as the vehicle’s original tires or another size recommended by the manufacturer. Look at the Tire and Loading Information label, or the sidewall of the tire you are replacing to find this information. If you have any doubt about the correct size to choose, consult with the tire dealer.”
Here is a copy of one of the NHTSA documents.
http://www.safercar.gov/Vehicle+Shop...ting/Tire+Size
When reading these posts it’s best to remember that I’m often writing from my point of view. Dissemination of government regulations and documents is not an easy task and many - me included - will sometimes draw conclusions that are not 100% truthful or factual. Whenever I’m in doubt or feel more information is necessary to the reader I’ll post the most current reference I can find or have in my files.
When large volumes of information became available and released to the WWW, government agencies jumped right on the bandwagon and downloaded almost everything they confirmed to be unclassified. But, would they make timely updates? It’s a toss-up. But, NHTSA has been very good so far as I can see.
I’m sure if you’ve read this far you know that there are DOT regulations for tires that are often talked about and quoted in all of the internet forum tire threads.
Have you ever asked yourself anything about such information and how it’s applied? Who is supposed to take action to insure information in such regulations is properly applied? Are we as end users supposed to take information from such regulations and use it to our advantage or disadvantage? For instance, this is a quote often used by tire thread participants referencing a DOT regulation. It is taken out of context from a large paragraph on the same subject.
“Except in the case of a vehicle which has a speed attainable in 2 miles of 50 mph or less, the sum of the maximum load ratings of the tires fitted to an axle shall be not less than the gross axle weight rating (GAWR) of the axle system as specified on the vehicle's certification label required by 49 CFR part 567.”
People will use that statement to justify their recommendation that a lesser load capacity tire can be used as long as it meets the requirement of the trailer’s GAWR. But wait, lets hash that over a bit. The DOT has presented the trailer manufacturer with a list of regulations they must abide by. That quote is from one of those regulations. If that regulation is directed at the vehicle manufacturer how come we, the private citizen have a right to apply it? Well, we don’t. No matter what is perceived by trailer owners about tire selection and fitment it still is in the hands of the trailer’s manufacturer. During the vehicle certification process the trailer builder is going to have to make a final selection on a number of items that are going to be put on the vehicle’s federal certification label and tires is one of them. Those certified tires are the minimum standard for that trailer. When it comes replacement time you can put on whatever your old buddy down at the local tire shop recommends or do some researching and use tires equal to the task certified on the vehicle’s certification label. With RV trailer tire replacements bigger - more load capacity - is always going to be better. Regardless of what you decide to use don’t pass-up an recommendation from the vehicle manufacturer. It’s always the first recommended place to ask questions. You may be surprised and find they have added an upgrade to your model line-up that supports a recommendation to another tire line.
Here is the list of regulations trailer manufacturers must apply when building your trailer.
https://docs.google.com/viewer?a=v&q...IyEkdLI94e_VGA
CW