subframes

Subframe refers to a secondary, rigid structural assembly that provides mounting points for major components and is attached to a larger main frame or body. In automotive engineering, subframes are common as front and rear modules that support the engine, transmission, steering, and suspension. They are usually bolted to the vehicle’s unibody or body-on-frame structure, allowing independent alignment and easier replacement after damage. Subframes are typically constructed from stamped steel, sometimes aluminum or composites, and are connected to the rest of the vehicle with rubber bushings or hard mounts to balance stiffness and vibration isolation. In unibody designs, the subframe functions as a detachable chassis segment: it carries the load path for engine and suspension while the body forms the rest of the structure. In body-on-frame designs, subframes may form almost the entire cradle for the engine and front or rear suspension.

Advantages include improved stiffness, modular repair, and reduced assembly complexity; they also allow different powertrain or suspension options with minimal changes to the main body. Disadvantages include added weight, potential for corrosion at fasteners, and the need for precise alignment during installation and repair.

Outside automotive contexts, the term subframe may describe any secondary frame that supports a subset of components within a larger frame, such as machinery mounts, crane bases, or building assemblies. It is typically designed to be removable or replaceable.