RV Tire Safety
with RV tire expert Roger Marble
I continue to read RV forum posts from people asking about what inflation to use. Tire sidewall, sticker, owner’s manual? The inflation used by a neighbor? There is also continued confusion on what the sticker inflation is.
The “vehicle certification label” aka the “tire placard” only considers one thing: the maximum tire load capacity (molded on the tire sidewall) when the tire is inflated to the level associated with the original tire load range (ply rating) as shown in the industry load and inflation tables.
Federal DOT regulations specify that the label indicate the tire inflation level needed to support at least 50% of the GAWR (gross axle weight rating). NOTE: There is no margin or reserve load capacity specified or required by the DOT regulations.
Starting in November 2017, the RVIA (RV Industry Association) required that trailers have a 10% margin on tire load capacity. Motorhomes do not have this margin requirement from RVIA as far as I know.
This reserve load margin for trailers is more important than on motorhomes due to the significantly higher interply shear imposed in trailer application.
Tire companies do not know the exact loading that will be placed on their tires in an RV application, so you have to do a little work to learn the minimum inflation needs for your personal vehicle. You could simply use the inflation on the tire placard, but you still need to confirm, with scale measurement, that no axle is loaded more than the stated GAWR.
It is also strongly recommended that you confirm your side-to-side load split is close to 50/50 as the tires do not “know” what the other tires are supporting, so you could be unknowingly overloading one tire by hundreds or even 1,000 pounds.
I have other posts in my blog on how to learn the individual tire loads.
Read more from Roger Marble on his blog at RVtiresafety.net.
 #RVT900
Seems you did not answer the question.
Roger said you have to know what load is put on the tires. To learn this you have to get the RV weighed by axle. That way you know the load on each tire. Only then can you answer the question, “How much air should I put in my tires?”
All this is fine, but I doubt anyone is going to have different tire pressures in each tire because they weighed their axles/tires individually and decided they needed to do this. I’m one of the lazy guys who puts a tad less than the tire pressure info on the sidewall of my tires (in my case 80 lbs).
Tommy, If you check out my RVTiresafety.net blog I have a number of posts on weight and inflation. The reason for weighing each end of each axle is to learn the load on the heavier end as very few axles are 50/50 end to end equal in load. Some RVs have one axle end 500 to even 1,000# heavier than the other. If you take the total axle weight and divide by 2 and use that figure and the inflation tables you will end up with one tire overloaded and more likely to fail. The other point is you do not inflate each tire to its load but all tires on an axle should have the same inflation. So you are inflating to handle the heavier loaded tire.
Your practice of running “a tad less” than the tire sidewall pressure may be OK but you might still be overloading a tire if the heavy end really needs 80 psi.
Tom Knowing the axle weight is good but not the best as axle loading is almost never 50/50 end to end. See my answer to Tom Molnar below for more info.