A self-sensing belt clamping device (10), for a safetybelt system is characterized especially by the fact that a car-sensitive locking body (48) and a belt-sensitive inertial system (90) are associated via a precontrol lever (44) directly with a rocking lever (38) and clamping member (26) and therefore can take effect without any substantial delay on the desired clamping of the belt, without having to apply a large initiating force by means of the sensor. Such a clamping device according to the invention can be independently arranged at any desired point between the door threshold and the deflector fitting in the B column. It can therefore be combined advantageously with a winder to form a winding clamp or with a deflector to form a deflection clamp.