superdave150

Some tire brands will not honor warranty unless you run max pressure. (A good friend experienced that with Carlisle.)

If the manufacturer lists inflation tables you're probably be safe following that method. Goodyear does, and I have followed that for years without a problem.

Some manufacturers specify adding extra 10 PSI for "sustained speeds over 65 MPH," even if that exceeds the number on the sidewall.

smokeywren

I have never seen a load/inflation table for Goodyear ST tires before now. I've looked and looked and searched and searched but I couldn't find one. But since you mention there was one available, I looked again. Goodyear hides it really good, but I finally dug it up:
http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf

A search on the Goodyear tire website won't turn it up. A search on the Goodyear truck tire website won't find it. Searching while looking at Marathon ST tires won't find it. It's hidden on the Goodyear RV Tires website.