I use a Topeak disc-specific rack on my non-disc road bike, as it gives me more clearance for a light mounted to my left seat stay, in addition to the light I run on the rear of the rack. I had to swap racks recently and now have a non-disc rack on my road bike, and the rack is touching the side of the light (Cygolite Hotshot), and if my fenders are clipped on, the fender support touches the top of the light.