Hi Tireman9. Let me put you to work here.
Replacement tires for the RV trailer.
Because of the load capacity differences between the ST and LT tires a lot of controversy presents itself whenever an LT tire is chosen to replace an ST tire.
Today many newer model trailers are equipped with 7000# axles and have ST tires rated at 3520# @ 80 psi as OE. A popular upgrade for those OE tires is the LRG 3750# @ 110 psi LT tire. It’s made by numerous off shore manufacturers and one here in the USA. My problem with that upgrade is the procedure. At 80 psi it only has 3042# of load capacity, so the recommended tire pressure depicted on vehicle’s tire placard at the maximum allowed is no longer valid. I’ve read numerous tire manufacturer SOP manuals and the section of the RMA manual that covers the procedure for setting a new recommended tire placard pressure. Hardly anyone supports my writings on this subject.
No matter where their wisdom came from the RV trailer manufacturer has set the recommended tire pressures. In their support is the DOT regulation. Therefore, the minimum load capacity for the OE tires was set with the recommended tire pressure found on the vehicle tire placard (3520#). It is my observation that the minimum tire pressure for the LRG tire would be what is required to attain the minimum load capacity of 3520#. That information should be noted in the vehicle owner’s manual and a notation made on or near the vehicle tire placard information.
In establishing a new recommended tire pressure for the replacement tires a very important factor needed for tire maintenance is also established. That is the point where one starts measuring pressure losses to evaluate a tire that is near, or in, a run flat condition.
Is that close enough or do I need to do some more work?
I know, I didn’t mention any reserves but none are actually required on the RV trailer axle (s) beyond GAWR unless provided with the OE tires.
So, what the heck, play it safe and add 12-15% with your replacement tires. That’s above GAWR.
FastEagle
