Tyre pressure and/or temperature sensor

A tyre pressure and/or temperature monitor 510 is arranged inside the tyre at one end of an elongate body which extends through a wheel rim 513. An antenna 515 is arranged outside the tyre at the other end of the elongate body. The antenna 515 is coupled to the monitor 510 by an inductive wire 512 which matches the output of the monitor to the antenna. Insulating material 511 surrounds the elongate body to prevent electrical contact with the wheel rim. The sensor may be a SAW (surface acoustic wave) sensor.