203mm Avid BB7 issue...
I have been working on switching over from my XT V-Brakes to a set of BB7's on the front (right now the rear will follow). After a little bit of tinkering I got the calipers installed and adjusted, took it for a little test spin and everything was great, the pads seemed a little sticky (partially because they were new, partially because I pulled them too hard initially and partially because I didn't have enough air in the new shock and the nose dove) but I was excited to have the new brakes on. The first time I rode them everything was perfect, no issues whatsoever. The second time riding the trails I noticed that when I turned sharply the disc would rub a bit, I think this can be attributed to a little bit of flex in the wheel since I am not exactly a light weight... again this was acceptable. However on my way home from the trail on the road we started picking up a little more speed and the disc really sounded like it was starting to drag. If I quickly squoze the brake lever the sound would go away for 20-30 seconds but then would come back. When I got home I started from scratch and completely refitted the brake, when I spin the wheel on the bike there is no sound at all, but after another pavement test ride once I get moving pretty quick the rotor sounds like it is scraping the pads again, but only when I am going quickly... ( I don't have a computer on my Mountain bike so I don't know the exact speed but I would think it's right around 15-16 mph.) Any ideas on what would cause this at higher speeds (and a straight line) but not lower speeds?
Older than dirt
It's caused by lateral flex in the front fork. 185's and 203's are more susceptible to it since they're further from the axle centerline. I have a Gary Fisher that does the same thing. You can sometimes back the pads off a touch more to help eliminate it but didn't totally alleviate it on mine.