A tire and wheel rim assembly having improved bead retention characteristics when run deflated.One or both bead seats is substantially straight and provided with an abutment respectively which is substantially continuous in the circumferential direction. Each abutment has a maximum radial dimension less than the minimum diameter of the tire bead reinforcement to allow fitment of the tire to a one-piece rim having a tire fitting well by conventional techniques. The taper of the bead seats is selected to enable abutments to be provided which have sufficient radial dimension or height relative to the adjacent bead seat such that under the action of road generated forces rotation of the tire beads about the adjacent abutment is effected to retain the tire beads at the bead seats.