Funny, Ive kept an old 75 rotor around just because of the nice aluminum center. I look at it but thats all so far. I did have two old front wheels (sold em) and seeing things like a custom XS which mimicked a 1915 flat tank board racer, Ive thought someone may want to machine that rotor center to mount a drive sprocket on ? 19's, skinny front & rear ? Just fun stuff. Now I want 5mm discs on my double disc "trailer queen" standard !