I've got a "new to me" 2008 K12GT. When I bought it the muffler was about a 1/4" from the rear tire and there were marks on the exhaust from the tire. I loosened the exhaust clamp, adjusted the gap between the tire and muffler and clamp to 1.5". After a few hundred miles the gap is less. I've done this twice. This can't be normal. Anyone ever see anything like this?