SAME thing happened to me.
Class C MH rode like a limo until the day I decided to treat her to brand new tires. :(
I put new Michelin's on and immediately the front end was ALL over!
Truck driver mechanic where I took it in to check the front end showed me how much that outer tread moved using just 2 of his fingers. I though I'd die when I saw how easy he could move that tread back and forth.
Too aggressive tread on the tires. They were flexing all over the place.
Hence forth why if you look at semi tires the outer tread is flat.