The perimeter disc brake rotors on the "Vinnie" I wrote about yesterday do a nice job of keeping the wheel open for a very clean look and one comment asked the question why more motorcycle manufacturers don't use them. Pretty good question in my mind since they seem to make a lot of sense and Buell is using them very effectively on their bikes. If you use only one disc you eliminate a lot of weight from the extra rotor, caliper, hoses and fluid, you lower the rotating mass and the position of the rotor would seem to make the caliper more effective. There may be some positive handling effects just from having the rotor out there to begin with instead of inboard, though that is outside of my knowledge, perhaps some engineers could weigh in on that one.
There have not been a lot of customs that I can think of with perimeter rotors, the bike built by LBF Cycles with the clear Lexan wheels had perimeter discs which they sourced from Krugger Motorcycles of Belgium, a custom builder who uses perimeter rotors on many of his bikes. After those and the Vinnie, who else?
When you look for aftermarket brake rotors, perimeter mounts don't seem to be available. I don't know where Matt Hotch got his, perhaps they were made just for him. Does Buell make their own? Hugo Van Waaijen, who works on the Bottpower project, pointed to Braking, a company over in Italy, that has an aftermarket kit with a 17 inch wheel and two perimeter disc brakes. Looks like a nice kit, something I haven't seen around anywhere else, though I really am not a brake expert so we're outside my area.
One thought I have is that perimeter rotors would have to be part of the wheel or mounted to a wheel with some attachment points built in and those are not available. No wheels, no brakes. But if they are effective, wouldn't some wheel builders respond or some brake companies ask a wheel builder to make them? How about a company like Performance Machine? They make wheels and brakes, seems like a natural next step.
Are perimeter discs available from more companies? If so, who? If they are, why aren't more builders using them? And, back to the original question, why aren't more manufacturers using them? Inquiring minds want to know.