Learned the hard way. After 15,000 miles my front Michelins are trashed. Due to improper alignment the inside tread cupped causing vibration at the steering wheel and unpleasant handling.
The E 450 cutaway is aligned perfectly at the factory, but a new alignment is needed once the chassis is built out. I found out that if you request this within the first few months of ownership it will be covered by warranty.
I ordered two new Michelins from Tire Rack, and took the motorhome down to the Ford Commercial Truck Service Center. They will mount the new tires and do the alignment ($255.00)
So word to the wise, after purchasing your new motorhome, get the alignment checked.