By Roger Marble
I have received questions on tire inflation from folks with small single-axle travel trailers, boat trailers and utility trailers. There is some confusion, which I understand, so let’s see if I can clarify my recommendations for inflations.
One common bit of information would be to learn the actual load on each tire position when the vehicle is loaded to the heaviest you ever expect it to be.
– For each axle identify the heaviest end and use that load when consulting tire Load & Inflation tables.
Motorhomes and trucks
These vehicles would use the heaviest axle end load when consulting the Load & Inflation tables.
– The inflation needed to carry or exceed the measured load would be your MINIMUM inflation.
– I suggest you select inflation that will provide at least 15% “Reserve Load” for your Cold Inflation Pressure. Some find it easier to go with a +10% inflation over the inflation in the tables.
– Just be sure you have some Reserve Load capacity.
– I see no problem with running higher inflation as shown on the “Vehicle Certification Label.”
Trailers with a single axle
– These can follow the same guidelines as seen for motorhomes.
Trailers with two or three axles
– Run the inflation molded on the tire sidewall that is associated with the tire “Maximum Load” capacity. Many RVs show that inflation on their label, but it is still a good idea to ensure you have a reserve load capacity. Some RV companies provide almost no load margin so it is up to you to make the appropriate adjustments. Running the tire sidewall inflation will give a lower Interply Shear force which, as you know, is a primary cause of belt separations on these RVs and is why tire life is about half what it is of comparable tires and loads on motorhomes.
– Select the heaviest load as measured on all four or six tire positions and confirm that the tire load capacity at the sidewall inflation provides at least a 15% Reserve Load.
For those interested in the science behind Interply Shear you might read this post.
Read more from Roger Marble on his blog at RVtiresafety.net.
##RVT 884
