A wheel with a rim having a drop center well and a retainer member for a tubeless pneumatic tire. In use the bead of the inflated tire is prevented from moving inwardly off the bear seat and into the drop center well of the rim by the retainer member which is fixed to the rim axially inwardly of and adjacent a bead of the tire. If during mounting and inflation of the tire a bead thereof becomes caught on the retainer, a gas bleed passage through the retainer prevents the tire from being inflated while the bead is caught thereon, thereby preventing damage to the bead of the tire and minimizing the risk of personal injury.