RV Tire Safety
with RV tire expert Roger Marble
As trailer owners start applying the new Goodyear Endurance ST tire, many are discovering that for some sizes the Endurance tire is only available in a Load Range that is higher than their OE tires. Some are concerned about what inflation to run. I have even seen some claim that running an LR-E at LR-D inflation, i.e., not at 80 but at 65, that the “tire will be overloaded, heat up and fail.”
While I understand some of the confusion, I do not agree with some of the concern or replies.
Tire load capacity is a function of the tire size and inflation level as long as you stay in the same “type” tire. By “type” I mean P type, or LT type, or ST type, or for large RVs, “truck” type.
If you stay with the same type and use the same numeric “size” then the only thing left to change is the Load Range or “Ply Rating.” While I do not like using Ply Rating as it is an old and discontinued nomenclature, it may help for better understanding in this post for you to think of the old term.
Important Point. “It is the air pressure that supports the load NOT the Ply Rating.” This statement is supported for every tire made by every tire company in the world through the use of Load and Inflation tables. These tables show a size and then for different levels of inflation the load capacity of that tire when inflated to that level. You will never see a tire shown where an LR-D at, say, 65 psi can support 1,500 pounds and for the same size the same tire when having an LR-E rating shown a higher load capacity at 65 psi. Not even just 1 pound more.
So an LR-E can support the same load at 50 psi as an LR-C, or the same load at 65 psi as an LR-D at 65.
You will not be overloading the LR-E if you load it to the 65 psi rating shown for that type and size tire and inflate it to 65 psi as you would for an LR-D. Since you are not overloading the LR-E tire it is not going to overheat at 65 psi with the 65 psi load, so the LR-E tire is not going to “overheat” at 65 psi any more than the LR-D will “overheat” if it is loaded to the 50 psi load rating and inflated to 50 psi.
When going to a higher “Ply Rating” you can then increase the CIP which increases the tire Load Capacity, which means it will actually be running cooler because of the greater “Margin.” The higher inflation will also lower the Interply Shear, which may lead to longer tire life.
When making the change you do need to confirm the upper inflation level for the rim. The wheel manufacturer should provide that information. As an alternative, the wheel will have a max load capacity stated. Looking at the OE tire size that comes on that wheel, look for the inflation that corresponds to that load and I would consider that to be the wheel inflation rating.
Read more from Roger Marble on his blog at RVtiresafety.net.