Abstract: Described are dropout assemblies for bicycles, which include a receiver and a dropout. The dropout assemblies can allow a single bicycle frame to be compatible with various drivetrains, wheels and other components and accessories. The receiver may include inner and outer mounting surfaces on which a dropout may be mounted. The dropout may include first and second mounting surfaces formed to be mounted on the inner or outer mounting surfaces of the receiver. The axle spacing may be adjusted by mounting of either the first or second surface of the dropout on the inner or outer surface of the receiver.