My bet is that this bike has t-boned something sometime in its career. It looks like an slight inward deformation which is exactly what my Trek 760 looks like after I hit something hard and then tried to straighten it with a Lil Brute frame straightener. End result is stretching the frame back into shape but "necking down" the tubing somewhere about the internal butting point. I love that Trek and its 531 tubing but, at 195 lbs, 7 years experience as a Schwinn mechanic, and about 10 more years in an engineering mechanics lab, that bike stays wall art FOREVER! John Wilson Sunny (for today, anyway) Southwestern PA