The multilink suspension design is the most advanced and functional independent rear suspension available for an automobile. It has all of the features of the double wishbone, but takes less space, generally weighs less, and is potentially more adjustable, especially if adjustable links are used. The idea of the multilink suspension is to use several short links to ensure that camber, caster and toe either do not change or change predictably when the suspension is compressed or extended.
Multilink suspensions typically come in three, four, and five-link models. Strictly speaking, any suspension design which utilizes three or more links is a multi-link. Consider the alternatives: The MacPherson strut suspension has two links, a lower control arm and a radius rod or tension control rod depending on who you talk to. Torsion beam suspension has one link (per wheel.) Trailing-arm suspensions have a single A-arm, and the related Weissach axle design has two links.
Four and five-link multilink suspension designs offer the greatest customizability. Adjustable links are readily available for most sports cars and can easily be made in any case, for example using threaded tubing. In the case of a five-link there are five separate rods, where a four link usually has an A-arm on the bottom, and upper, upper front, and upper rear links. If adjustable upper front and rear links are used, the toe angle can be changed by adjusting them. If an adjustable upper link is utilized, then the camber can easily be changed. Using either dual adjustable lower arms (in a five link) or an A-arm whose two inboard attachment points can be moved in and out will allow you to adjust the caster angle. This allows a degree of customization not available on any other type of suspension. In addition, multilink suspension nearly always utilizes a coil-over design for springs and damping, which also allows the greatest control over the ride of the vehicle.
The only drawback to the multilink design is increased complexity and hence more potential points of failure, and increased cost. However, through the use of polyurethane bushings, the lifetime of suspension components can be extended dramatically. The smaller size of the links generally saves considerable weight as compared to a double wishbone design.
Multilink suspensions are usually mounted to a subframe which bolts to the bottom of the car, though on a full-frame car they might be connected directly to the chassis. As they are usually used on unibody vehicles a subframe is nearly mandatory. The upper mounts for the shock absorbers may be integrated into the unibody or implemented as part of the subframe. The subframe is usually attached to the unibody through bushings which are a potential source of wheel hop and spacers (or washers) are sometimes used to compress the bushings to reduce flex, or the bushings may be replaced with metal bushings which result in transmission of greater vibration into the body, but completely eliminate flex between the body and subframe. They are primarily used in rear suspensions but may sometimes be found in the front as well.