A subframe is a structural component of a vehicle, such as an

automobile A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...

or an

aircraft An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...

, that uses a discrete, separate structure within a larger

body-on-frame Body-on-frame is a traditional motor vehicle construction method whereby a separate coachwork, body or coach is mounted on a strong and relatively rigid vehicle frame or chassis that carries the powertrain (the engine and drivetrain) and to wh ...

unibody A vehicle frame, also historically known as its ''chassis'', is the main supporting structure of a motor vehicle to which all other components are attached, comparable to the skeleton of an organism. Until the 1930s, virtually every car had ...

to carry specific components like the

powertrain In a motor vehicle, the powertrain comprises the main components that generate engine power, power and deliver that power to the road surface, water, or air. This includes the internal combustion engine, engine, transmission (mechanics), trans ...

drivetrain A drivetrain (also frequently spelled as drive train or sometimes drive-train) or transmission system, is the group of components that deliver mechanical power from the prime mover to the driven components. In automotive engineering, the driv ...

, and suspension. The subframe is typically bolted or welded to the vehicle. When bolted, it often includes rubber bushings or springs to dampen vibrations. The primary purposes of using a subframe are to distribute high chassis loads over a wide area of relatively thin

sheet metal Sheet metal is metal formed into thin, flat pieces, usually by an industrial process. Thicknesses can vary significantly; extremely thin sheets are considered foil (metal), foil or Metal leaf, leaf, and pieces thicker than 6 mm (0.25 ...

of a monocoque body shell and to isolate vibrations and harshness from the rest of the body. For example, in an automobile with its powertrain contained in a subframe, forces generated by the

engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ge ...

and

transmission Transmission or transmit may refer to: Science and technology * Power transmission ** Electric power transmission ** Transmission (mechanical device), technology that allows controlled application of power *** Automatic transmission *** Manual tra ...

can be sufficiently damped to prevent disturbing the passengers. Modern vehicles use separate front and rear subframes to reduce overall weight and cost while maintaining structural integrity. Additionally, subframes benefit production by allowing subassemblies to be created and later introduced to the main body shell on an automated line. There are generally three basic forms of the subframe: # A simple "axle" type, which usually supports the lower control arms and steering rack. # A perimeter frame, which supports the lower control arms, steering rack, and engine. # A perimeter frame with full support, which supports the lower control arms, steering rack, engine, transmission, and possibly the full suspension, commonly used in front-wheel-drive cars. Subframes are typically made of pressed steel panels that are thicker than body shell panels and are welded or spot-welded together. Hydroformed tubes may also be used in some designs. The revolutionary monocoque, transverse-engined, front-wheel-drive 1959 Austin Mini set the template for modern front-wheel-drive cars by using front and rear subframes to provide accurate road wheel control while maintaining a stiff, lightweight body. The 1961 Jaguar E-Type (XKE) used a tubular space frame–type front subframe to mount the engine, gearbox, and long bonnet/hood to a monocoque "tub" passenger compartment. Beginning with the 1960s, subframes saw regular production with

General Motors General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. The company is most known for owning and manufacturing f ...

' X- and F-platform bodies, and the Astro/Safari mid-size vans. Subframes are prone to misalignment, which can cause vibration and alignment issues in the suspension and steering components. Misalignment is caused by space between the mounting bolts and the mounting hole. Several companies in the automotive aftermarket, including TyrolSport in the US and Spoon Sports in Japan, offer solutions for subframe misalignment and movement issues.

References

{{Reflist Automotive chassis types Auto parts Structural system Structural engineering