Connecting device for connecting a pneumatic tyre inflation valve to a compressed air source, wherein the tyre valve is optionally a Dunlop valve, a Schrader valve or a Presta valve, each of which comprising a valve stem in which a valve element is received defining an air inlet, wherein the connecting device comprises a hollow body in which a hollow space is formed and which comprises a compressed air connection for connection to a compressed air source, wherein in the hollow space a pressure chamber is formed which is in flow communication with the compressed air connection, wherein the hollow body comprises a valve receptacle into which the valve stem of the tyre valve can be inserted with its free end leading in a first direction along an axis, wherein the valve receptacle comprises a sealing with a central opening, which sealing is disposed in the hollow body and encircles the axis, wherein the central opening is connected to the valve receptacle and to the pressure chamber, wherein the encircling sealing is arranged to cooperate with the valve stem of the tyre valve (25, 26, 27) which is inserted along the axis into the valve receptacle in order to connect the pressure chamber and the air inlet of the tyre valve (25, 26, 27) in an airtight manner with each other, characterized in that a piston is disposed in the pressure chamber which is displaceable along the axis relative to the hollow body, which displaceable piston is biased by a spring element in a second direction opposite to the first direction into a first position in such a manner that upon insertion of the Presta valve or insertion of the Dunlop valve into the valve receptacle the free end of the inserted tyre valve (25, 26) gets in contact with the front end of the piston and can displace the piston from the first position in the first direction against the return force of the spring element, wherein the piston is configured to provide for flow communication between the air inlet of the inserted Presta valve or Dunlop valve and the pressure chamber when the piston is in contact with the free end of the inserted Presta valve or Dunlop valve, and wherein the piston is disposed in the pressure chamber to be further displaceable in such a manner that the piston can be displaced in the second direction by the supply of compressed air in the second direction, wherein the piston is configured to cooperate with the valve element of a Schrader valve inserted into the valve receptacle and to place the valve element to an opening position when the piston is displaced in the second direction by the supply of compressed air, wherein the piston is configured to provide flow communication between the air inlet of the Schrader valve and the pressure chamber when the piston has placed the valve element to the opening position. wherein the connecting device comprises a hollow body in which a hollow space is formed and which comprises a compressed air connection for connection to a compressed air source, wherein in the hollow space a pressure chamber is formed which is in flow communication with the compressed air connection, wherein the hollow body comprises a valve receptacle into which the valve stem of the tyre valve can be inserted with its free end leading in a first direction along an axis, wherein the valve receptacle comprises a sealing with a central opening, which sealing is disposed in the hollow body and encircles the axis, wherein the central opening is connected to the valve receptacle and to the pressure chamber, wherein the encircling sealing is arranged to cooperate with the valve stem of the tyre valve (25, 26, 27) which is inserted along the axis into the valve receptacle in order to connect the pressure chamber and the air inlet of the tyre valve (25, 26, 27) in an airtight manner with each other, characterized in that a piston is disposed in the pressure chamber which is displaceable along the axis relative to the hollow body, which displaceable piston is biased by a spring element in a second direction opposite to the first direction into a first position in such a manner that upon insertion of the Presta valve or insertion of the Dunlop valve into the valve receptacle the free end of the inserted tyre valve (25, 26) gets in contact with the front end of the piston and can displace the piston from the first position in the first direction against the return force of the spring element, wherein the piston is configured to provide for flow communication between the air inlet of the inserted Presta valve or Dunlop valve and the pressure chamber when the piston is in contact with the free end of the inserted Presta valve or Dunlop valve, and wherein the piston is disposed in the pressure chamber to be further displaceable in such a manner that the piston can be displaced in the second direction by the supply of compressed air in the second direction, wherein the piston is configured to cooperate with the valve element of a Schrader valve inserted into the valve receptacle and to place the valve element to an opening position when the piston is displaced in the second direction by the supply of compressed air, wherein the piston is configured to provide flow communication between the air inlet of the Schrader valve and the pressure chamber when the piston has placed the valve element to the opening position.