difference between car frame unibody vocabulary

Body-on-frame VS Unibody

Posted: by David Sastre

The Body-on-frame vs Unibody is an old topic. But why we have always this discussion? Let’s see what are it functions, benefits and weak points. Both provide habitability for the passengers and support for all components of the car. Components such as the suspension system, engine, brake system, steering…

Those two chassis are the most known vehicle frame types.


But let’s go into details for Body-on-frame vs Unibody…
What are the main differences between the Body-on-Frame and the Unibody?

Definition of the frames


As the name suggests, in this construction the body is built on a relatively rigid frame. This frame supports the drivetrain and the engine.
In this design, the frame resists more torsional flexing before yielding than other frame types.
The Body-on-Frame is easier to design, repair, and is less likely to suffer damage from rust. On the other hand, this design is heavier and has higher center of gravity. The higher center of gravity can compromise the road performance or handling.

Unibody Frame

In this frame, both functions are met in the same assembly. Nowadays, the unibody assembly is the most common frame type. Certainly it is for passenger vehicles. Its success among the others, is due to its lightness.

Even popular midsize SUV’s, have acquired the unibody frame construction. Recently SUV’s switched from the body-on-frame to the unibody construction.

The monocoque or unibody construction has reached the state of art in the automobile manufacturing. Is so sophisticated that the windshield often makes a significant contribution to the vehicle’s structural strength.

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