Why Tanks Don't Use Wheels And Tires

The very concept of an "armored vehicle" has been around for at least as far back as 1482, when Leonardo da Vinci penned a letter to the Duke of Milan that included a design for what is considered a proto-tank — one of many inventions you may not have realized came from da Vinci. It had an odd conical shape that da Vinci figured would deflect enemy fire, with holes for guns and cannons to fire through. It was also equipped with interior wheels that very much resembled the setup for the automobile, which was still centuries away from being invented.

However, the first working tank — known as "Little Willie" — didn't appear until 1915 (during World War I). It was built after Winston Churchill established a committee to find a solution that would overcome trench warfare, a military tactic that had created a deadly stalemate. "Little Willie" was constructed by placing an armored car body onto a Killen-Strait tractor already equipped with tracks, which, given the combat scenario, worked perfectly for this particular battlefield. 

Large, heavily armored tanks with a turreted canon aren't equipped with wheels because tracks evenly spreads the vehicle's weight over more surface area. These tracked weapons platforms are better suited for cross-country mobility and provide far better traction on rough terrain. They also keep the tank from losing traction, sinking or becoming stuck, which would have almost certainly happened in the trenches of WWI if those first tanks had been equipped with wheels instead.

Even so, there's still a debate over whether or not wheels or tracks are better for an armored vehicle because there are certain types that do use wheels effectively, like the General Dynamics Piranha V, the M1126 Infantry Carrier Vehicle (ICV) known as the Stryker, and the Rheinmetall Boxer. What's better depends entirely on the battlefield scenario and where that scenario is being played out in the world. 

There's no arguing that tracked vehicles have far better traction than those equipped with standard wheels. However, there's also no question that wheels move a vehicle significantly faster than tracks, particularly on hard-packed surfaces and conventional roads, which many of today's battlefields contain. Additionally, tires don't tear up and destroy whatever they roll over, no matter how heavy the vehicle is. Most combat vehicles that use wheels aren't equipped with heavy armor or a main cannon and are used in different capacities. 

Another factor to consider is the "rolling resistance" these armored vehicles create while traveling on standard roads, and there's actually a mathematical formula the military uses to determine this number. A tracked vehicle's average "rolling resistance" equals 4% of its weight, but a wheeled vehicle with cross-country tires is just 2% of its weight. Thus, vehicles with wheels require less fuel and can cover more distance by road. That advantage becomes moot when they go cross-country, where they may require more fuel than a tracked vehicle.