Recently, the occurrence of vibration issues, referred to as hot judder, has become increasingly prevalent in disc brakes during high-speed braking. However, the automotive industry still does not fully understand this phenomenon, and clear countermeasures have not yet been taken. This study aims to clarify the mechanism behind hot judder by analysis modeling it as a self-excited vibration, driven by time delays induced by disc deformation due to heat. The dynamometer test rig reproduces hot judder, and the experimental results are qualitatively compared with the analysis results. It was observed that while the number of hot spots varies with the disc rotation speed, their generation frequency remains constant regardless of the number of hot spots and consistently matches the system’s natural frequency. Additionally, hot spots form in regions where disc expansion is most significant, directly contributing to the occurrence of hot judder. Furthermore, by analyzing the amplitude growth of a specific number of hot spots, it is discovered that as the speed decreases, the number of hot spots increases, with each hot spot undergoing repeated cycles of growth and decay.