immobilization of the support on the wheel rim is therefore excellent whereas in units where the same element provides both the seal and the support vibrations and or centrifugal force can cause rocking of the supports which themselves cause breaking of the seal it has thus been found that it is very advantageous to separate the immobilization functions on the wheel rim and the seal actually the mechanical stress of the seals alters over time their sealing performance the sealing means used here consist of two lips 21 and 22 of which one lip 21 is integral with upper section 23 of locking element and of which the other lip 22 is integral with outside cylindrical face 24 of the locking elements the first 21 of these lips is intended to rest on shaft 1 of support 1 and the second 22 is intended to rest on wheel rim 3 the first lip 21 therefore assures the seal between shaft 10 and locking element 2 and the second 22 between locking element 2 and wheel rim 3 the inflation pressure itself reinforces the seal thus achieved because it acts on a single face of the lips moreover since lips 21 and 22 are easily deformable they assume slight.