CDB disc brakes out perform drum brakes because they have greater thermal capacity and discs are far more resistant to heat checking than drums. Brake performance is related to duty cycle. Each time the brake actuates, it generates heat. How well the brake handles the heat through absorption and dissipation determines the brake’s performance.
Instantaneous energy absorption is related to a brake’s swept friction area. Energy dissipation is related to the percent of swept friction area that is exposed to air.
CDB brakes typically have 20% more swept area and more than twice the exposed swept area of the drum brakes they replace. Discs rarely heat check. They absorb heat from both sides at the same rate. This results in an even rate of expansion across the thickness of the disc.
Heat checking of drums is the result of thermal shock. When a drum brake is applied, the OD of the drum heats up; however, the ID remains cooler. This results in thermal gradient across the rim which produces extreme mechanical forces. These forces cause heat checking.