A device for inserting and extracting a support ring in a tyre

The device comprises a base (4) for positioning a tyre and a lever (6) pivoted on a support (5) and able to move and be fixed in position along a plane which is radial with respect to the centre of the base. An active end (6a) of the lever (6), located on an L-shaped bend at an end of the lever (6), can be introduced internally of the opening to interact contactingly with the internal surface of a part of the support ring pre-inserted in the opening. By acting on the lever (6), the active end presses the ring against the inside of the tyre with radial force. The support ring is of a type which when applied on a vehicle wheel enables the vehicle to continue moving for a considerable time even where tyre pressure is suddenly lost.