A tundra tire is a large rubber tire used on light aircraft that are flown in remote locations. The necessity of landing on unimproved runways—often consisting of little more than an open patch of rough ground—require that the plane be able to absorb the bumps. To counter the effects of these makeshift runways, the tundra tire is mounted on the aircraft. The under-inflated, over-sized tundra tire acts like a sponge and soaks up the bumps to make landing and takeoff possible from remote locations.
Looking much like a large doughnut, a tundra tire is often inflated to just slightly more than flat status. The soft design of the tire allows it to cushion the airplane as it rolls over very rough terrain by flexing and floating on the surface. If the tire were to be inflated similar to the tire found on a family automobile, it would bounce violently off of the bumps and rocks and cause the airplane to careen off course and ultimately crash.
In snowy areas, the tundra tire is often accompanied by a set of skis. The inclusion of skis allows the plane to land on snow or icy ground, depending on the circumstance. Bush pilots began using truck tires on their airplanes in an attempt to soften the landings and takeoffs in the rough country. While the truck tires helped somewhat, their construction required they be inflated too much to really do the trick. Eventually, an over-sized flotation-type tire was used and has evolved into the tundra tire.
Made of a lightweight rubber, the tundra tire is not constructed with as many plies as a family automobile tire. This maintains flexibility and softness in the tire's sidewall. The lightweight design also allows the aircraft to fly without an increase in weight. Some pilots do note an added resistance due to the over-sized tundra tire catching so much wind, however.
Many expeditions and explorations into very difficult country have been made possible thanks to the tundra tire. Hospitals and emergency life-saving equipment can now be made available to many remote locations. The tires have also made it possible to evacuate sick and injured people from areas that would certainly be unreachable by any other method. Not just rough and rocky terrain is accessible to the tires—soft wetlands are also easily treaded upon with the tires. In the spring wet season, the flotation tires glide across swamps and saturated ground with little resistance.