A bicycle comprises a main frame and a suspension assembly coupled to the main frame. The suspension assembly includes a dynamic crank support and a spring mechanism. The dynamic crank support is movable from an uncompressed position to a compressed position. The spring mechanism biases the dynamic crank support toward the uncompressed position. The suspension assembly further comprises a dynamic seat support coupled for movement with the dynamic crank support. For example, the dynamic seat support and the dynamic crank support can be rigidly coupled to each other and cooperatively form one bar of a four-bar linkage. An eccentric assembly is supported by the main frame and rotates about a first axis. The eccentric assembly pivotally supports the dynamic crank support for rotation about a second axis offset from the first axis. The spring mechanism preferably comprises a spring secured between the main frame and the eccentric assembly to rotationally bias the eccentric assembly.