Abstract: A modular storage system for use with a bicycle can include a rail coupled to the top tube of the bicycle and at least two rigid compartments or modules releasably coupled to the rail. Each of the rigid compartments has an interior compartment accessible while a rider is riding the bicycle. Each of the rigid compartments can be shaped to have low aerodynamic drag. Each rigid compartment can be configured to hold at least one of a fluid container, food, bicycle repair implements, a replacement tube, and a replacement tire.