A pressure relief device (100) for an inflatable tire comprises a body (102) having a chamber (116) therein and pressure relief mechanism for releasing air when the air pressure in the chamber exceeds a first predetermined pressure level. A conduit (108; 208) inter-connects an air inlet (110; 210) with an air outlet (112; 212). The conduit (108; 208) is provided in a pin (104; 204) arranged to slide axially in a passageway (106) in the body, the pin (104; 204) extending from the air inlet (110; 210) to the air outlet (112; 212) and being slidable between a first position in which it cannot release a stem of the tire, and a second position, in which it can release the stem.