RV Tire Safety: Tire load capacity is like your engine red line

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By Roger Marble
Many times people point to regulations for tire inflation and say that RV companies select the tire inflation, and that is what they should run because they think that is the “optimum” inflation.

Well, the reality is that the “Load & Inflation” tables actually are giving you the MINIMUM inflation needed to support the stated load.

First, we need to remember that the load is not your estimate or the load your brother-in-law has in his RV, but the actual measured load that you can only learn by getting on a truck scale.

Here is a comment on tire load capacity:

“You might have a valid point if the discussion were about OEM tires. However this discussion is about new tires on an existing TT. The owner should go through the process that the TT manufacturer did when determining tire pressures. Tire pressures should be set based upon the tires and their actual loads.

“Unfortunately, TT manufacturers don’t have actual load information, so they base pressures on max load. The TT owner has (or should get) information that the manufacturer does not have: actual load. That information should be used to determine optimal inflation pressures.”

As a tire engineer I would be happier if people understood that the inflation given in the Load tables are the MINIMUM needed to support the stated load.

In the non-RV world, tire inflation is not based on the minimum needed to support the load. You will find that most cars have inflations that provide a Reserve Load of 20% to 25% or more. That is one reason car tires have such a low failure rate compared to tires in RV application.

Some people want to believe that all is good as long as you meet the minimum standard, then they are surprised when tires fail. Well, they fail due to the cumulative damage done to the structure when used. This damage reduces the load capacity because damage weakens the structure.

It has been shown that a hard hit from a pot hole can effectively “kill” a tire, with the only question being how long can you travel before it finally dies. I have also posted that you can hit a pot hole hard enough to “fatally” damage a tire yet have no recollection of the hit.

Your car or truck has an engine “red line.” Think for a moment about how long your engine would live if you ran it at 95% to 98% of red line speeds all the time. Well, that red line is like the inflation number in the tables in reverse. Running at the red line is like running at the maximum load capacity for your tire for the inflation shown in the tables.

I bet most of you run no higher than 75% to 80% of red line on your engine, if that high. That gives you a 20% reserve. Maybe you should consider doing the same for your tires.

 

Read more from Roger Marble on his blog at RVtiresafety.net or on RVtravel.com.

 ##RVT973

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