A subframe is a structural component of a vehicle, such as an automobile or an aircraft, that uses a discrete, separate structure within a larger body-on-frame or unit body to carry certain components, such as the engine, drivetrain, or suspension. The subframe is bolted and/or welded to the vehicle. When bolted, it is sometimes equipped with rubber bushings or springs to dampen vibration.
The principal purpose of using a subframe is to isolate vibration 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 two 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 subframe is usually made of pressed steel panels which are welded or spot welded together. The use of Hydroformed tubes may also be used.
The sub frame saw regular production in the 60's and 70's General Motors X and F cars.