One of the first things that came to my mind was if it had ST tires. We had Duro tires on our Cameo ( switched to G 614s). The second year we almost lost two on the same day with huge sidewall bulges. I just don't have faith in ST tires at their 65 mph rating much less at 77 mph. Too many other variables as well. Are the tires at the right inflation, bearings greased, brakes good,tires cracked or old, etc. I've had to do very hard braking going around 40 and I near soiled by trousers. At 77 how long will it take you to do a emergency stop?
Why push that knowing what they're rated at?? At 77 mph a blown tire on a raised trailer with a short bed 1/2 ton pickup? I made sure I kept my distance behind him. After reading many posts here I'm reconsidering my 65-68 traveling speed. This speed seems to keep in in a good power range. I will try slower on my next 5 hr trip in July.