Run-flat tire

[1] In 1934, Michelin introduced a tire that was based on technology developed for local commuter trains and trolleys.

It had a safety rim inside the tire which if punctured would run on a special foam lining.

While the tire performed as advertised it was far too expensive to be a feasible option for most private automobile users.

Most recently, Bridgestone and Pirelli run-flat tires are supplied on some new model BMW cars.

Pressure Zero Tire (PZT)[4] was pioneered by American Engineering Group (AEG) for US Special Forces.

AEG prototype dissipates heat and has the tire flexibility and strength to support the heavy military pick-up weight while providing a relatively smooth ride.

The run-flat insert has an unsurpassed ability to carry heavy vehicle loads for long distances at high speeds.

The basic benefit of using run-flat tires is continued mobility in case of a loss of air pressure, due either to a "normal" puncture or to a hostile deliberate act including a bullet strike while the vehicle is traveling at high speed.

In 2006, it was expected that such tires would gain popularity with armored vehicle manufacturers, but growth figures were slow with one major model, the Michelin PAX System, no longer being developed by the manufacturer (though replacements will be produced for the foreseeable future).

[5] Former US President Barack Obama's presidential limo, "the Beast", had Goodyear Kevlar lined run-flat tires.