The Effect of Rotor Crossdrilling on Brake Performance

A review of available information on the effect that brake rotor crossdrilling has on brake performance reveals a wide range of claims on the subject, ranging from ‘minimal effect, cosmetic only’ to substantially improving brake cooling and fade resistance. There are also several theories on why brake rotor crossdrilling could improve fade performance, including crossdrill holes providing a path for ‘de-gassing’ of the brake lining material and increasing the mechanical interaction, or ‘grip’ of the lining material on the rotor.

This paper reviews three case studies in which the opportunity arose to compare the performance of brake systems with crossdrilled versus non crossdrilled brake rotors in otherwise identical brake corner designs. The effect of brake rotor crossdrilling on brake cooling, brake output, brake fade, wet brake output, and brake wear rates were studied using both on-vehicle and dynamometer data. Some data were generated comparing the interaction effect on brake performance between brake lining material and brake rotor crossdrilling; however most of the study focuses on the effects of rotor crossdrilling with a single lining material. Where possible, evidence in the test hardware, the test data, and brake corner design features are related in an attempt to understand the mechanisms by which crossdrilling affected brake performance. Conclusions are drawn based on the data generated and observations made with the brake systems of the three case studies.