I was bobtailing in a single axle semi yesterday down the interstate at 70 mph when the 3ft chrome exhaust stack on the top side of the muffler along side the cab decided to come off and flew back and hit the one drive tire. The tire catapulted it forward and it passed the truck up and all I seen was a quick glimpse of something shiney out my window. I knew I didn't hit any thing cause I didn't hear any thing. Well a few miles down the road I was at my destination and decided to look if I lost any thing. Sure enough the stack was gone and the tire had a big chunk out of it. I did go back and find the $130 chrome pipe and slavaged it. I was lucky it didn't come thru the rear cab window.