Developing a brake system with high overall customer satisfaction rating is a constant challenge for OEMs as well as their brake suppliers. Brake system performance is directly linked to the engagement between the rotors and pads. The materials for the rotors and pads play a key role in the nature of the engagement. Therefore, to meet the performance targets, it is critical to have a good understanding of the brake rotor materials and their impacts.Gray iron is the most widely used brake rotor material in the industry owing to its superior thermal handling capacity, damping characteristics, and wear and cost advantages. G30 per ASTM A48 is generally specified for most brake rotors with minimum tensile strength of 200 MPa and Brinell hardness of 187∼241. G20 is also widely used for brake rotors, especially for brake smoothness and optimal lining life.This study has found that variations in gray iron material can considerably affect brake fiction coupling behaviors and hence the overall brake performance. Rotors that meet both physical property and chemical composition requirements in general can deliver very different brake performance due to variations in rotor friction surface characteristic and microstructure of rotor material. The suitability of microstructure and control of friction surface characteristics are the most important aspects for gray iron material in dictating overall rotor performance.