The Sno-Train and the Overland Mark 2 tires garnered a great deal of attention. Why shouldn’t they? the Firestone 120x48x68 tires are 4 feet wide and 10 feet tall. They were inflated to 20psi at the factory, but more commonly at around 7 to 10psi depending on terrain conditions. In this image, you can just make out the walking beam connecting the two tires together on the Mark 2.