A friend of mine has a Cannondale F700 with a front disc brake and a rear V. He wishes to switch to a rear disc as well, but his wheels have 4 holes instead of the normal 6. From what I see this appears to be another proprietary Cannondale thing. The LBS quoted him $205 for a back brake which seems pretty high and he doesn't want to spend that much. Do any other companies sell discs that work with these wheels? He doesn't care too much if they are mechanical or hydraulic.
The 4 bolt rotors are going on ebay for $9.99, but they are 171mm. Will these rotors work with other disc brakes like Avid mechs?