Wheel unit

A wheel unit comprising a wheel rim, a pneumatic tyre receivable on the wheel rim and a runflat assembly adapted to be seated on the wheel rim to close off a well provided in the wheel rim, the runflat assembly including an annular support body which is radially expandable to an expanded condition and contraction means adapted to be operated via an opening formed in the wheel rim, the contraction means, when activated, being operable on the support body to cause the support body to be contracted to a radially contracted condition, the support body, when in its expanded condition, being located within the tyre during fitment of the pneumatic tyre on the wheel rim and, on completion of fitment of the tyre, the contraction means being accessible through the opening to permit operation of the contraction means to cause the support body to be radially contracted to seat the runflat assembly on the wheel rim to close off the well, the support body, when in its contracted condition, having a diameter greater than that of the wheel rim.