Rick, you said your loaded weight is 11,100 lbs., that comes to 2,775 lbs. per tire. Useing Glenn's educated guess method ( which I agree with ), 72 psi sould be adequate pressure. If you are not showing unusual wear patterns, and your tires are not overheating, you should be ok. I think the dealers insist on 80 psi just so there is no chance of tire failure due to underinflation. IMHO, just another case of CYA.
On Edit - I should also say, I have mine set at 80 psi., mostly because I do NOT trust ST rated tires. The sooner I change them out, the better I'll feel.
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