A pneumatic tire is disclosed to run while flat without the tire coming off the wheel rim and without excessive heat due to the friction from the rubbing of the sidewall portions. A circumferential locking lug on the sidewall exterior adjacent to the rim flange locks over the flange when the tire goes flat, keeping the tire on the wheel rim. To improve stability and to cushion the load while running the tire flat, inserts of cord material or hard rubber may be inserted into the sidewall, or the sidewall thickness may be increased with concentric slots added. Internal friction is decreased by coating the interior of the sidewalls with a lubricant.