You guys seem to have it figured out but let me put the icing on the cake.
Yes it is the air pressure in the tire that carries the load not the tire itself.
The Load/Inflation tables provide the MINIMUM cold pressure to use to support the measured load.
You really should have a margin on the tire load capacity. By regulation passenger tires require at least 9% above the max load for the vehicle. Since R service is almost always at or real near (or over
) the max load rating of a tire I STRONGLY suggest TT should have at least a 15% margin. in load capacity.
Again multi-axle TT are a unique animal so there are special considerations if there is a real engineer (not one that plays one on TV
Whenever you make a turn, gentle or 90 degree backing, you are placing unique and high loads on the TT tires that your TV tires do not get exposed to. This because the tires are not rotating with their center-line
pointing to the center of the radius.
This results in high "Interply Shear" You can read this Google on "interply shear tires
" to learn more.
You can not eliminate this force unless you made the axles "steer" which is $$$$
You can lower the shear by increasing tire inflation.
So if you are running LR-D tires and only need 55 psi to support the load what should you do?
1. At least increase the inflation to 65. This will give you better load margin and will lower the interply shear.
2. To further decrease the shear you would need higher inflation i.e. 70 or higher.
You will not decrease your chance of Tread Separation by putting on LR-E tires but only running 65 psi. In fact putting on LR-E may cause other problems because the construction in a LR-E tire may be heavier which means more heat which is what accelerates the degradation of the belt rubber.
Back to my reccomendation.
Know your actual tire load. Individual tire info is best as few axles are 50/50 side to side.
Also few TT have 50/50 axle to axle load split.
Select the heavier end of an axle and use that number when consulting the Load tables to learn the MINIMUM inflation needed.
This inflation would be the Warning level on your TPMS.
Add at least 10% with 15% better to the inflation to provide a load capacity margin.
BUT if we really want to lower tire failure probability Increase the inflation to no less than the sidewall inflation. If that doesn't give you a 15% margin then go up in Load Range.
As you can see there are a number of items to be considered and selecting the inflation is a balancing act.
You note I didn't mention wheels. You must have wheels capable of supporting the heavier load. You should also have wheels that are rated for inflation at least equal to your cold inflation level.
All tires on an axle MUST have the same inflation. On multi axle trailers I suggest all tires have the same inflation.
OK so have I overloaded you enough?