Abstract: In a wheel angular acceleration sensor for an anti-lock controller for sensing the locking tendency of a vehicle wheel being braked on the basis of overrunning and attendant axial displacement of a flywheel to produce a control signal for a braking force, the flywheel is connected through a clutch and a cam mechanism with an output shaft rotatable in accordance with rotation of the wheel, the cam mechanism being operable in response to overrunning of the flywheel to provide an axial displacement to the flywheel and comprising a drive cam plate supported on the output shaft through a bearing against axial movement and a follower cam plate connected to the flywheel and adapted to cooperate with the drive cam plate.