Tire overloading on curves....

[Tireman9]

RE margin on load capacity.

There is no requirement for "overload capacity" above what you see when you do a static measurement. The big issue with the small margin the RV company supplies is that they have cut the margin by assuming perfect 50/50 load balance between TT axles plus perfect 50/50 side to side balance on each axle of every RV.

Having said that, you should realize that some tire companies such as Carslile I believe, actually suggest a 20% margin on static measurement. Federal regulation requires a 6% minimum on Passenger cars and most cars have a side to side balance very close to 50/50 as they don't have equipment in them like RVs do.

The big issue IMO is that only a very small % of the RV trailer owners have ever checked the individual tire loads. THIS link or the worksheet on THIS link have instructions on how to do the math if you can't get to a large RV event where individual scale readings are offered by RVSEF or similar organization.
It is well documented that a majority of RVs have one or more tires and/or axles in overload when static weights are measured.

We see some folks get 4, 6 or 7 or more years service out of their tires while others are hard pressed to get 2 or 3. IMO one of the major reasons is that even with all RVs subject to curve and wind side loading that some folks have a reasonable margin (15% or greater) while others are in overload when parked. I think we all can understand that the lower the margin the more likely you are to have a failure.

The info on curve and wind just identifies why it is so important to know you have a reasonable margin. You need to remove some of those bowling balls out of your RV to improve your margin AND you need to confirm you have a margin on each tire when stationary not just a theoretical margin arrived at by just dividing the total tire load by the number of tires.
Some large RVs have been identified to have imbalance in the range of 1,000# Other RVs have been identified to even be in overload when they leave the factory.

I suggest that for MH that after confirming the actual load on each tire that the heavier tire load be used to establish the MINIMUM cold inflation and that a +10% increase in inflation be used for the "Set pressure". Personally I run +20% above the minimum needed to support the measured load of the heavier side of my MH.
Remember to never exceed the rim rating for load or inflation.

For TT you need to confirm you are not in static overload Plus due to the unique side loading you need to run the tire sidewall inflation to try and lower the Interply shear that is working to tear the belts off your tires PLUS you should have a 15% margin of load capacity at that sidewall pressure.

You can google RV tire Interply shear to learn more on that scientific fact.

[Ky-N]

Originally Posted by Tireman9

RE margin on load capacity.

I suggest that for MH that after confirming the actual load on each tire that the heavier tire load be used to establish the MINIMUM cold inflation and that a +10% increase in inflation be used for the "Set pressure". Personally I run +20% above the minimum needed to support the measured load of the heavier side of my MH.
Remember to never exceed the rim rating for load or inflation.

Good luck finding rims rated for the higher loads and pressures very few sites list the load capacity and NONE that I have found list the PSI rating. And I agree with the statement on axle overload, our trailer has a gvwr of 3510# riding on a 3500# axle.

[Tireman9]

Originally Posted by Ky-N

Good luck finding rims rated for the higher loads and pressures very few sites list the load capacity and NONE that I have found list the PSI rating. And I agree with the statement on axle overload, our trailer has a gvwr of 3510# riding on a 3500# axle.

Well my MH has the standard rims used on C3500 & C4500 GM cutaway vans which come with LR-E tires even though I don't need 80 psi in my tires. I am inclined to believe that other Class-C are similar.
TT owners need to contact the wheel mfg and learn the max rating but in most cases TT placard specs the max tire pressure.

While some want simple answers about changing tires there are many things to consider if you want to avoid problems. There is no single answer that will work for all RVs.

RE your GVWR... Have to wonder how the "engineers" at your RV company managed to calculate all the components to be that close or do you think they might just have decided to say the GVWR was 3510 so they would be in compliance with the regulations? I'm sure that no one in the RV industry would ever do that.