Thermal capacity, or heat storage capacity, is determined by how much weight or mass is located in the outer ring section of the disc. This is the area where the friction surface of the disc meets the internal vanes. The more mass located in this area, the more thermal capacity a disc has. Factors contributing to a disc's thermal capacity are: mass, annulus, disc width, air gap, vane design, and the disc material's thermal properties.
Brake systems are designed to operate best within a prescribed temperature range. While modern high performance friction materials broaden this temperature range, it is critical that the brake disc in a system has adequate thermal capacity. Once the thermal capacity of a disc has been exceeded, the excess heat "spills over" to other braking components, resulting in loss of braking force (brake fade).