The purpose of this paper is to modify bitumen using crumb rubber and simultaneously partially replace fine aggregates using coconut shell charcoal in the base course of a flexible pavement. The samples are made with different combinations of bitumen modified with 5%, 10% and 15% crumb rubber by weight of bitumen while simultaneously replacing the fine aggregates with 5%, 10% and 15% coconut shell charcoal by weight of fine aggregates. The samples are tested for maximum stability using the Marshall stability test. The sample providing the maximum stability is taken as the result of this paper.