A take-apart tire and wheel assembly including a multi-piece wheel rim having axially spaced bead flanges, a rim base, and a pneumatic tubeless tire, preferably adapted to removably receive in its tire inflation chamber a safety runflat insert. The wheel assembly also includes a safety vent for preventing inflation of the tire cavity in the event of improper assembly or disassembly of the safety tire and wheel assembly, including an O-ring seal disposed in a triangular cavity formed between opposing portions of rim segments of the wheel assembly, and mounting studs and associated nuts that releasably clamp the rim segments together with the O-ring captured in compression therebetween. The outboard wheel rim segment includes a wheel mounting disc and may also have a safety inflation valve coupling fixed to the outboard rim segment. An interior air passage of the coupling communicates with the tire cavity and has a minimum cross sectional dimension which prevents insertion therethrough an air inflation valve provided on an inner tube of sufficient size to fit within said tire cavity and capable when inflated of rendering said wheel and tire assembly normally operable for supporting its normal vehicle load in a run-mode of the vehicle.