This is a hands-on demonstration. Try this with your friends, and be prepared to explain the physics of the demonstration to them. The pressure of a tire on the road should be approximately the same as the air pressure in the tire.
Work Step by Step
You may find that the pressure of a tire on the road is greater than the air pressure in the tire. This is because the walls of the tire are rigid, and help hold up the vehicle. If the tires were floppy-walled balloons, the 2 pressures would be the same. In an extreme example, the air pressure inside could be zero if the tire walls were stiff enough.