A sub-frame arranged to be mounted on a chassis of a car and to have the rear wheels of the car mounted thereon is arranged to receive an electric drivetrain arranged to drive the car. The sub-frame includes a cage including bars arranged to form an upper perimeter and a lower perimeter and a plurality of struts extending between the upper and lower perimeters; a pair of rear wheel suspension mounts, each rear wheel suspension mount being arranged to have one of the rear wheels of the car mounted thereon; and a plurality of brackets located on the cage and arranged to facilitate connection of the sub-frame to the chassis of the car and/or to the electric drivetrain. A frame and vehicle including such a sub-frame and a method of installing such a sub-frame are also disclosed.