By Roger Marble
Are RV trailer tires exempt from the physical laws of the universe? What is so special about RV trailers that would make people think they are free from scientific principles and physical realities?
On an internet forum for owners of a well-known RV trailer company, there was a discussion on what the correct or proper inflation and load capacity was for tires on the company’s trailers. I jumped in with the following observations.
Tires list the maximum load they are rated to support and they also list the minimum cold inflation needed to achieve that load capacity. This dichotomy of “The Maximum is the Minimum” was covered in my blog on RV Tire Safety.
I really do not understand why people seem so afraid of running more than the minimum cold inflation needed to support the actual load.
I am in the process of working through the “Rule Making” documents from DOT when they set the minimum margins on inflation for cars, SUVs and trucks equipped with TPMS. It is noted that RVs were specifically excluded from this rule making. Could that be because the RV companies didn’t want to see any increase in costs even if it meant the product would have fewer failures?
No, that couldn’t be. No corporation would ever shave costs if the safety of the product might be compromised – would they?
The MINIMUM cold inflation a tire should have would be the level needed to support the actual tire load. They also established that the normal cold inflation should be at least 25% higher than the MINIMUM. Their objective was to minimize tire failures that might result in damage or injury. The DOT knows that tire pressure increases with temperature (2% per 10 F), and tire engineers know and design, and even depend on, this physical fact.
For some reason people feel it’s OK to have zero margin in their RV trailer tires. It wasn’t until 2017 that RVIA (RV Industry Association) started to specify a small 10% margin. Some people argue that the RVIA is not a real requirement as it isn’t a legal requirement. For RVs built before 2017, many RV trailers have certification stickers that specify ZERO margin or essentially zero margin as the tire capacity that was to be considered acceptable.
With the above as guidelines, I have to wonder why people continue to complain about having tire failures. You are making the conscious decision to ignore established engineering recommendations and safety margin guidelines. So, again, just what is so special about RV trailers that would make you think they are exempt from scientific principles and physical realities?
Have a tire question? Sign up for Roger Marble’s new Facebook Group: RV tire news, information and discussion, moderated by Roger. He’ll be happy to help you.