The present invention relates to a mounting/demounting tool unit for mounting a tyre to or demounting a tyre from a rim of a vehicle wheel and for being adapted to be attached to a tyre mounting/demounting machine, including: a longitudinally extending tool carrier arm having a center line and a first as well as a second end, a mounting/demounting tool having a first as well as a second end and a hook arranged in the region of the second end, and being pivotally mounted to the tool carrier arm in the region of its first end, wherein means for reversibly urging the mounting/demounting tool in a resting/operating position and for positioning the mounting/demounting tool in said resting/operating position are provided.