Yes, I'm flummoxed! It did it initally right after I put the pedals on (about 60 miles of riding) and I noticed as I pedaled it out of the crank, a bit of the black material of the pedal 'post' or what ever it is had eroded off. I cleaned it up and the threads themselves didn't look damaged so I put it back on and tightened it up. This time it lasted about 300 miles before it worked itself loose again. Seems like maybe it's not staying tight because the threads of the pedal might be damaged (hard to see because the post is black). Very strange and dangerous if it keeps doing it. Can I use lock-tite (or whatever it is) on it?