A damper for a bicycle, having a primary unit including a damper tube, a piston rod that supports a main piston, a reservoir tube that is outside of the compression chamber of the primary tube, and an inertial valve within the reservoir tube. The damper also includes a flow path connecting the reservoir fluid chamber and the compression chamber of the primary tube. The damper also may have a damping valve in the reservoir tube. When the inertia valve is open, the damping valve opens before flow through the inertia valve is maximized. The main piston and the damper tube at least partially define a compression chamber and a rebound chamber. The main piston is movable within the damper chamber of the primary unit. The reservoir tube includes a reservoir fluid chamber. The inertial valve is responsive to terrain-induced forces and not responsive to rider-induced forces when the shock absorber is assembled to the bicycle.