Originally Posted by PSFORD99
Many of us are running other size tires ,and weight ratings on our fifth wheels. All of my fifth wheels have had ST235/80/16's either E rated or Grated, and I have upgraded to ST235/85 /16's G rated . Although I don't run max inflation, nor follow a weight chart . I run my G rated tires as said before @ 95-100, and have done so without issues for many years.
When tires of the same designated size are used as replacements with a higher load range letter, it is not a tire size change, just a load capacity increase making the increase in load capacity optional above the cold inflation pressures recommended by the vehicle manufacturer.
When a designated tire size differs (ST235/80R16 replaced with ST235/85R16) the 85 is a “plus sized” tire. Tire industry standards for using plus sized tires can be found in numerous PDF files. Basically the new cold inflation pressures are set from the load capacity the OE tires provided on the vehicle certification label. Replacement tires MUST provide a load capacity equal to or greater than what the OE tires provided – via inflation.
The use of a supplemental tire sticker for plus sized tires is authorized by NHTSA and highly recommended. Here is a picture of one. In place of load index the load range letter is used for ST or LT tires.