I didn't have any vibrations or anything from them, it rode just as good as it did on the 17s.
My only worry on the back is that the 285/50 is like 31" tall. There is plenty of room width wise.
The front for me was tight on both sides, sounds like your clip might be crooked maybe? Here's the only picture I have of the rolled fenders. I used a friend of mines Eastwood fender roller to do it.
This was before with the trim, I haven't put that back on yet.
