Gold Rush 203mm disk rotor clearance with chainstay
Notice that the rotor has at times gouged a groove in the chainstay (that I've subsequently filed smooth and polished). The clearance with the chainstay at the edge of the rotor is about 3mm. The wear on the chainstay was observed after rear brake use that caused loud howling and vibration. I suspect the edge of the rotor moved out of plane while vibrating, causing the chainstay gouge, there being no other plausible explanation (e.g. loose bearings, rotor mount, caliper alignment) for how the edge of the rotor could move closer to the chainstay.