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

automobile A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarde ...

or an

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engine ...

, that uses a discrete, separate structure within a larger body-on-frame or

unit body 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 a ...

to carry certain components, such as 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 ...

, drivetrain, or

suspension Suspension or suspended may refer to: Science and engineering * Suspension (topology), in mathematics * Suspension (dynamical systems), in mathematics * Suspension of a ring, in mathematics * Suspension (chemistry), small solid particles suspende ...

. The subframe is bolted and/or

welded Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as braz ...

to the vehicle. When bolted, it is sometimes equipped with

rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, an ...

bushings or springs to

dampen Damping is an influence within or upon an oscillatory system that has the effect of reducing or preventing its oscillation. In physical systems, damping is produced by processes that dissipate the energy stored in the oscillation. Examples incl ...

vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, su ...

. The principal purposes of using a subframe are, to spread high chassis loads over a wide area of relatively thin sheet metal 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 and transmission can be damped enough that they will not disturb passengers. As a natural development from a car with a full chassis, separate front and rear subframes are used in modern vehicles to reduce the overall weight and cost. In addition a subframe yields benefits to production in that subassemblies can be made which can be introduced to the main bodyshell when required on an automated line. There are generally three basic forms of the subframe. # A simple "axle" type which usually carries the lower control arms and steering rack. # A perimeter frame which carries the above components but in addition supports the engine. # A perimeter frame which carries the above components but in addition supports the engine, transmission and possibly full suspension. (As used on front wheel drive cars) A subframe is usually made of

pressed steel ''Pressed'' is a 2011 Canadian crime drama film directed by Justin Donnelly and starring Luke Goss, Tyler Johnston, Jeffrey Ballard, and Michael Eklund. It is the debut directing project for Justin Donnelly. Plot Business executive Brian Parker ...

panels that are much thicker than bodyshell panels, which are welded or spot welded together. The use of

hydroformed Hydroforming is a cost-effective way of shaping ductile metals such as aluminium, brass, low alloy steel, and stainless steel into lightweight, structurally stiff and strong pieces. One of the largest applications of hydroforming is the automot ...

tubes may also be used. The revolutionary

monocoque Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, ...

transverse engine A transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the direction of travel. Many modern front-wheel drive vehicles use this engine mounting configuration. Most rear-wheel drive vehicles ...

front wheel drive Front-wheel drive (FWD) is a form of engine and transmission layout used in motor vehicles, where the engine drives the front wheels only. Most modern front-wheel drive vehicles feature a transverse engine, rather than the conventional longitu ...

1959

Austin Mini The Mini is a small, two-door, four-seat car, developed as ADO15, and produced by the British Motor Corporation (BMC) and its successors, from 1959 through 2000. Minus a brief hiatus, original Minis were built for four decades and sold during ...

, that set the template for modern front wheel drive cars, used front and rear subframes to provide accurate road wheel control while using a stiff lightweight body. The 1961 Jaguar E-type or XKE used a tubular

spaceframe In architecture and structural engineering, a space frame or space structure ( 3D truss) is a rigid, lightweight, truss-like structure constructed from interlocking struts in a geometric pattern. Space frames can be used to span large areas with ...

type front subframe to mount the engine gearbox and long bonnet / hood, to a monocoque 'tub' passenger compartment. The subframe saw regular production in the 1960s and 1970s General Motors X platform and F platform bodies and the 1985-05 M platform vans (

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, Safari). 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 chassis-subframe mounting bolts and the mounting hole. There are a number of companies in the automotive aftermarket that offer solutions for the subframe misalignment and movement issue, including TyrolSport of the US and Spoon Sports of Japan.

References

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