This is incredibly interesting to me. I knew motorcycles could get headshake in certain circumstances, but I had no idea bicycles could. With that said, I don't trust my Lynskey Backroad at more than about 37. It starts feeling, for lack of a better word, light in the the front end. Like if I pushed it, It would lose stability. I have run a lot of bikes over 40 and have bumped 50 once. I never felt anything other than perfectly planted. For those of you who have experienced it, did it feel glued to the road one second and the next it started the wobble, or did it telegraph that it was entering an unhappy zone.