So what is the difference is a unibody frame and a space frame? Well, they are very similar, as they are both a unibody, which means one. This is because all of the parts of a vehicle, such as the frame rails, fender aprons, rocker panels, pillars, floor pan, etc., are all welded together making one piece. A space frame consists of parts welded together making one unit as well, but a space frame does not depend on any outer panels for strength. In other words, you can take all of the outer parts, fenders, roof, doors, quarters, and deck lid and the space frame will still have it’s full integrity. If you think of a race car; it’s a frame with a lightweight body sitting on it. The body is only for looks, as a race car will still have all it’s frame strength without the body on it.
Unibody – Frame and body is one piece. Additional strength is added by some of the outer panels.
Space Frame – Frame and body is one piece. – No additional strength is added by outer panels.
Here is a quick video from Audi, which describes their aluminum space frame structure. This will help you understand the concept of a space frame structure.
Here is a video of a funny car. You will see the body lifted up by one person while another person checks something on the motor before the race. It is easy to see that the body is nothing more than a lightweight skin. This is a good example of a space frame.
So there you have it….the difference between a unibody and space frame.