A bicycle including a frame having a main frame portion and an articulating frame portion pivotally mounted to the main frame portion and carrying a rear wheel of the bicycle. A shock absorber preferably is operably connected between the main frame portion and the articulating frame portion. Preferably, the top tube and down tube of the main frame contact one another for a distance extending rearwardly from the head tube of the main frame. In one arrangement, the down tube has a non-circular cross-sectional shape.