A few of them, too:
1) Why does the 747 have the outter main gear, (under the wings), hang down so much, they are nearly vertical. I would think this would make it harder for them to be stable, but obviously not.
2) Why does the A340 have a centered landing gear that's behind the two others, I would think it hitting the runway first would cause a lot of pressure to sit on it and cause some stress.
3) Will any airplane ever have more than two front wheels besides the Myria 225?