The self-stabilising dynamics of bicycles

Abstract

We analyse the classical problem of the stability of bicycles when moving quickly and upright. Developing a lean causes the front wheel to turn thereby setting the bicycle instantaneously into circular motion. The centripetal force associated with the lean-dependent turning circle gives a restoring torque which corrects the lean. The force also helps self-steer the front wheel, ensuring the bicycle continues in an essentially straight path. We give the frequency of lean oscillations about the vertical executed during riding. As in the literature, we discuss the neglect of gyroscopic effects, which experiment suggests are negligible.