Photo courtesy Caterpillar The Caterpillar-sponsored No. 22 car

The original races were run on dirt tracks that got rutted and bumpy. The unmodified cars were not tough enough for this type of abuse, so NASCAR began allowing modifications to the stock cars to increase their durability. Over the years, more and more modifications were made, sometimes to increase safety (see How NASCAR Safety Works for details) and sometimes to improve competition. NASCAR strictly controls all of these modifications, which are spelled out in detail in the NASCAR rule book. Cars are checked for compliance with these rules at every race.

Today, NASCAR race cars have very little in common with street cars. Almost every detail of a NASCAR car is handmade. The bodies are built from flat sheet metal, the engines are assembled from a bare block and the frame is constructed from steel tubing.

In this article, we'll see how these race cars are made, starting with a component that is key to the drivers' safety and provides the foundation for everything on the car: the frame.