Just a little foot note here, when reinstalling a thrown tire lay the engine top down in a soft cradel and stretch the tire around the wheel grove using a small common screw driver.
If it dose not snap into place, or if it seems loose and flimsy throw it away.
If the tire dose snap smartly into the grove you can apply a little Super Glue under it by lifting up the tire using the little screw driver to pull up on it so as to allow application of the glue with the tubes needel tip.
After you do that run the engine upside down in the cradel and then let the spinnig tire run under the flat face of your screw driver. This will spread the glue under the tire. Do not run the engine fast, about five to ten miles per hour will do.
Let the glue set for a few hours and then run your trains. I have found that by doing this I have gotten three or four times the use out of my tires.
If you don't have a suitable replacment tire see the Dennis technique above.