Independent suspension is an automobile suspension system that allows the wheels on a hub to move independently of each
other. Each one goes up and down without affecting the other. This is contrasted with a beam axle, live axle or deDion system in which they are linked - movement on one
side affects the wheel on the other side. Most modern vehicles have independent suspensions on the front wheels.
Many vehicles also have an independent rear suspension (IRS). IRS, as the name implies, has the rear wheels independently sprung. A fully independent
suspension has an independent suspension on all wheels.
Independent suspension typically offers better ride quality and handling characteristics, due to lower 'unsprung weight' and the ability of each wheel to
address the road undisturbed by activities of the other wheel on the vehicle. Independent suspension requires additional engineering effort and expense in
development versus a live axle or beam axle arrangement. A very complex IRS solution can also result in higher manufacturing costs.
Some early independent systems used swing axles, but modern systems use Chapman or
MacPherson struts, trailing arms, multiple links, or wishbones.
The key reason for lower 'unsprung weight' relative to a live axle design is that, for driven wheels, the differential unit does not form part of the
unsprung elements of the suspension system. Instead it is either bolted directly to the vehicle's chassis, or more commonly to a subframe.
The relative movement between the wheels and the
differential is achieved through the use of swinging driveshafts connected via universal (U) joints,
analogous to the constant-velocity (CV) joints used in front wheel drive vehicles.