Why do landing gears smoke upon impact during landing?

Introduction
Have you ever gone bird watching? If you have, then you have obviously seen airplane landing gears smoking while touching down on the ground. Some people think is the impact that causes a temporary fire that lights on and off. Or is the air in the tires being squeezed out during impact? Let's find out.

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So... Why does this happen?
The answer is very simple. The landing gears are only used during takeoff and landing. They do not move within the flight. On long-haul flights, 98% percent of the time the landing gear remains stationary. Wo why does it smoke upon impact? Is it too dry? No. They smoke upon impact because once the plane is about to land, the landing gear is lowered. Though it is lowered, it will still remain stationary whatsoever. Once the plane's landing gears touch down, due to the sudden speed that is put on the tires, they smoke and then adjust to the speed of the aircraft.

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Why don't they explode?
You might be wondering... Why don't airplane tires explode under the weight of the aircraft, the impact against the ground? But guess what? The secret is not the material of the tires, but the type of air inside the tire. Airplane tires are filled with nitrogen because it takes more energy to make nitrogen react than air. This means that it takes more force to make a nitrogen filled tire to explode than it takes to make an air-filled tire to explode.

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When do they explode?
They most likely won't. There is only a 0.001/100000 chance. Usually, when the force starts getting close to making the tires explode, the gear holders collapse. This means that the metal sticks holding the landing gears collapse. So under most occasions, the landing gears don't explode.There is also a feature called a shock absorber that will absorb the impact. It is used on all commercial and passenger aircraft.

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On the right, there is a passenger landing gear diagram. For a more clear picture, visit this link:

https://goo.gl/z9cPhQ