<p>Grey cast iron (GCI) is widely used to manufacture brake discs, owing to its superior friction properties, thermal stability, and damping characteristics. Graphite flakes within the GCI pearlitic matrix are preferred for braking applications. However, uneven cooling during rotor solidification can induce residual stress, leading to disc distortion and thickness variations in the subsequent ferritic nitrocarburizing (FNC) treatment. These residual stresses can increase the out-of-tolerance scrap rate and adversely affect rotor functionality. Stress relief (SR) heat treatment is employed to mitigate these stresses and enhance dimensional stability. This investigation examined and compared the effects of SR heat treatment and natural ageing on the damping characteristics, natural frequency, and hardness of GCI brake rotors prepared for subsequent ferritic nitrocarburization (FNC) and correlated these critical properties to the GCI rotor microstructural characteristics. The findings indicated that the SR treatment marginally reduced the hardness but did not significantly affect the microstructure, natural frequency, or damping characteristics. The damping properties of SR Discs A and B demonstrated modest improvements of 11.8% and 2.8%, respectively, attributable to the enhanced matrix ductility resulting from the SR heat treatment, which facilitated dislocation movement. A comparative analysis of the bulk hardness and microhardness of the treated and naturally aged discs revealed minor decreases of 4.6%–5.2% and 5.2%–7.2%, respectively, in the SR rotors. This investigation underscores the significance of SR heat treatment in optimizing GCI brake disc manufacturing for FNC processing and enhancing performance and geometric stability without compromising critical properties, such as resonant frequency and damping characteristics.</p> Graphical Abstract <p></p>