An automatic shoe clearance adjustment apparatus having a ratchet wheel 124b and a driving member 127 comprising a pawl section 127f making a ratchet engagement with the ratchet wheel 124b and an arcuate leaf spring section 127e developing a resilient force for adjusting the automatic shoe clearance adjustment apparatus. The leaf spring section 127e is made of bi-metal. When the temperature of the leaf spring section 127e exceeds the predetermined degree, the arcuate leaf spring section 127e thermo-deflects so as to weaken the resilient force, thereby the automatic shoe clearance adjusting operation is suspended.