Troy-Bilt 1909975  Friction Drive Disc

The purpose of a Friction Disc in most cases is to slow or stop the motion of the drive shaft, and consequently the wheels from rotating. This is most often found in self-propelled snow throwers and walk-behind mowers or riding mowers. In some uses, like in snow throwers, a friction wheel contacting the friction disc and shaft can transmit motion from the motor to the axle. Grease and other contaminates which reduce the force of friction can all impair the effectiveness of this friction-based system.