Make a bold speed reduction and note the fuel use. It will be much better. Air resistance is exponential and at 75mph is 133% of what was at 65mph and 225% of 50mph. ST tires are rated for "the speed limit" according to my inquires. Proper tire pressure is paramount -- inflate to maximum sidewall pressure but age is a factor as well. Note my experience indicates travel trailer tires often have no excess capacity. No penalty fitting larger capacity tires. I violated my own rule regarding replacing Special Trailer tires ever four years and paid the penalty of a blowout (not mere flat) at the speed limit on the Ohio Turnpike late last summer. Not a question of tire pressure as they'd been verified at 50psi less than an hour earlier. Aborted the trip, fitted five (5) new wheels and tires, bought a good jack, and continued the trip without incident. Trailer wheel/tire shop complimented me on my driving skill handling the explosion. Must have been the Expedition 'cuz all I did was slowly pull over onto the shoulder. -- Chuck PS: Those paved shoulders on the Turnpike are heavy with rocks and gravel as I discovered on my belly changing the wheel! But at least there are shoulders. Virginia thinks a white line and trees are just fine.