Consists of two overlapping, crossed control arms of equal length and a bridging component connecting their ends (their other ends connect to the chassis). The latter is also the spindle for the wheel itself, or carries it. Viewed from the side of the vehicle, the trailing arms overlap forming an 'X' shape. The various components connect to each other as well as the chassis through hinges.
1. Rear wheel can oscillate up and down without also experiencing appreciable horizontal displacement, either lateral or longitudinal, throughout its full range of vertical travel.
As the wheel travels vertically the control arms also rotate upwards or downwards and cause the spindle mount to be rotated as well, either towards the front or the back of the vehicle. However, the midpoint between the two hinges on the spindle carrier, which the trailing arms connect to it by, describes a nearly straight line.
This is the intentional result of the careful choice of specific components and their respective relative lengths (distances between hinged connections) and the relative positioning of the linkage's attachment points on the chassis.
2. Enables a passive rear-wheel steering effect by seamlessly and gradually exchanging wheel camber angle for wheel toe-out or toe-in angle, throughout the wheel vertical travel.
3. Simplicity and compactness.
Passive wheel steering and camber angle decrease effect is achieved by positioning the suspension linkage's attachment points on the chassis such that the plane the suspension moves through (when accommodating the wheel's vertical travel) is tilted laterally inwards (towards the vehicle center line) while the wheel spindle is itself slanted downwards relative to the bridging component and so that same plane, when the suspension is in neutral position within its range of vertical travel, such that the wheel itself has a camber angle (at that point where the suspension is in neutral or default position) which is the combination of the negative camber angle of the suspension linkage assembly (with respect to the chassis) and the positive camber slant of the spindle relative to the bridging component – which we can refer to as spindle carrier if it's a separate component that the spindle itself is rigidly attached or connected to.
Because the spindle carrier swivels, throughout the entirety of the suspension's range of vertical travel – which can be up to nearly 180 degrees of rotation in a plane parallel or nearly parallel to the vehicle's center-line – the wheel spindle is itself rotated nearly 180 degrees in that same plane as well. Which changes the wheel spindle's downward slant, when the suspension is in the neutral or default position, into either negative or positive toe angle, as the wheel ascends or descends from its designed neutral or default position.
As the spindle's tilted mounting on the spindle carrier only fully compensates the suspension linkage's negative camber when the suspension is in neutral or default position, the wheel also gradually gains a negative camber which grows more pronounced as the suspension travels further away.