A safety insert or roller for inflatable tires comprising a plurality of arcuate members having detachable and pivotal clamping engagement adapted to form a ring closely engaging the drop center of a tire mounting rim and protruding beyond said rim a substantial distance in the direction of the tread of an inflated tire mounted thereon. At least the inner and outer peripheries of the assembled ring are of rigid plastic material, preferably having lubricant properties, such for example as highdensity polyethylene. Connecting structure between said inner and outer peripheries can be of the same material or a different material such as formed metal, and is fashioned to provide a combination of low weight and high tensile and compression strength. Overlapped end portions of the arcuate members when loosely joined together permit relative swinging movement facilitating assembling the device within a tire while half mounted on a rim; and the fastening means for adjacent ends of the arcuate members including bevelled means for providing circumferential clamping of the assembled ring in the tightening thereof.