Its just a hunch. I get a "feeling". The faster i go the more i feel it. Ive only had it a month and a half. Seems to be more noticible. I dont hear anything. I had the back wheel up and spun it as well as the front, and heard nothing but brake pad noise (normal). Im pulling the rear wheel off to check the bevel and grease it (and the wheel bearings). If i see nothing ill pull the swing arm to check the ujoint. I also plan to look under the boot and see if i can detect any play. Hope its nothing further in the case.