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Friday, January 15, 2021

Are RV trailer tires exempt of the physical laws of the universe?

In 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 companies trailers. I jumped in with the following observations.

Tires list the Maximum load they are rated to support and tires also list the minimum cold inflation needed to achieve that load capacity. I have covered this "The Maximum is the Minimum" dichotomy in this 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. I note 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 10F) and tire engineers know and design and even depend on this physical fact.

For some reason people with RV trailers feel it's ok to have zero margin. It wasn't till 2017 that RVIA started to specify a small 10% margin and 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. What is so special about RV trailers that would make you think they are exempt from scientific principles and physical realities?

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