OK Bingo, I'm fixin ta chime...........DING...DING...DING
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Bob, just because the Goodyear G614 tire is rated for a maximum air pressure of 110 psi, doesn't mean it requires 110 psi. You need to weigh the trailer axles while it is hooked to the truck. Each axle individually would be ideal. Use that weight to calculate the air pressure for each axle. Michael's formula looks like it should work just fine.
Another thing Bob. Your axles may be rated for 6750 lbs each, but that doesn't mean your tires have to be rated for 3375 lbs to be safe and legal. Again, the ONLY way you are going to know, is to weigh the trailer.
As far as the Mission ST235/80R16E goes, I set them at 80 psi and constantly worry about them flying into little pieces. Because of what they are, not because of air pressure. Sometime this week, or this weekend I am going to replace them with LT235/85R16E Bridgestone Duravis R500 commercial light truck tires. They also will be set at 80 psi, and I won't worry one bit about them.