I have developed this "roaring" noise usually when braking but I have heard it occassionally when I am accelerating. It appeared around 2k as I was accelerating. I was not hard on the throttle either. It does not happen everytime I brake and seems to be related to the lean of the bike. The noise seems to pulse and is speed related. I'm wondering about bearings but don't really know. My bike has stage 1. I recently had the belt tightened up but think the noise was there before the belt adjustment. I am running a Michelin Commander on the back and a Metezeler on the front, different tread patterns. Any ideas??