Lower temperatures at the sliding interface of a disc brake will reduce thermal wear and fade tendencies of friction materials. One method for achieving these lower temperatures is to improve the thermal design of gray cast iron discs.The purpose of this investigation was to study design improvements of brake discs for trucks. To accomplish this objective, an analytical thermal model was developed. The model employed the lumped parameter approach, in which the disc was subdivided into a number of small volumes. The model specifically simulated disc temperature response during 80.5 km/h (50 mph) fade tests performed on a dynamometer. The thermal model was correlated with test data to verify and improve its accuracy, and then utilized to evaluate effects of geometry changes.Results showed that mass concentration in the disc faces yields lower temperatures at the friction interface through 10 successive snubs. Even after a very large number of snubs, temperature cycling would be less extreme with thicker faces.The study has demonstrated that thermal modeling is a valid and potentially valuable tool in the design optimization of brake discs. Indeed, the analytical approach, combining both thermal and stress analyses, along with prototype testing, may prove the most effective method for future design development of disc brakes.