230 miles and this knock sound starts at the seat-stay to link pivot. The bolts are/were all tight. I can recreate it by grabbing the front brake with my left hand and the top of the rear tire with my right hand and moving the tire side-to-side. I confirmed it's that's the problem spot by loosening that pivot...and with it loose...no knocking. Torque it to spec and it starts knocking again. Arghhhh. Suggestions?