Ordered a Primary Drive 520 X Ring chain to replace the lovely stocker. I had heard about the fatter chains hitting the case but this chain didn't hit the case so I thought that I was OK until I saw this, http://i13.photobucket.com/albums/a270/briggl/chiangrind2.jpg http://i13.photobucket.com/albums/a270/briggl/chaingrind1.jpg after about 8 rides. Major grinding on the inside of the frame just below the sub frame connection. Before the flaming starts I religiously kept the chain tension in spec and usually a hair on the tight side. So I called Rocky Mountain and they said that they would take the fat chain back and replace it with the same chain without the X rings. You may want to check your bikes if you are running a wider chain. I am thinking about crafting some kind of steel guard plate that I can bolt onto the frame by way of the opposite side of the subframe bolt hole. Any fix suggestions are appreciated.