Bought Avid BB7s for my bike. Front is fine. Rear caliper hits spokes when mounted directly to frame. Dback/Raleigh suggested checking sheldonbrown.com and am awaiting response from him. LBS couldn't solve the problem. I've been told that this is a 1999 frame and disc brake tabs weren't standardized then. What adapter/bracket do I need or isn't this possible to do? Thanks for any suggestions.