When it comes to calipers, are they sized according to rotor diameter? What I want to do is use Cobra brakes on a 15" wheel but the Cobra brakes will only fit in 17" wheels. Can I use a 11.75" rotor disc brake upgrade and fab a way to bolt the cobra calipers on or will they only work on the larger rotors? Has anyone else ever done this or seen it done? Any reply would help. Thanks in advance.