The Audi S4: Dynamic Suspension

Source: Audi AG

The dynamic suspension of the new Audi S4 and S4 Avant is based on the layout that has made the A4 the sportiest car in the midsize class. Numerous suspension components made of aluminum reduce unsprung masses. The five-link front suspension can handle longitudinal and lateral forces separately; a firmly mounted subframe ensures exceptional rigidity for the front section. The springs and shock absorbers of the self-tracking trapezoidal rear suspension, which permits a wide luggage compartment thanks to its compact design, are aligned separately to improve response.

In keeping with the dynamic performance of the S4 and S4 Avant, the suspension has been retuned. Stiffer bearings for the control arms guarantee elastokinematics for a sporty performance; lateral and camber rigidity are clearly enhanced. The minimal body movements lend the S4 and the S4 Avant maximum stability, even when braking. The shock absorbers have firmer settings and the body has been lowered by 20 millimeters (0.79 in).

Handling precision – without compromise

All these measures lend the S4 and the S4 Avant the driving dynamics of a sports car – their reactions are smooth, almost reflex-like; handling precision knows no compromise. The steering connects the driver with the road to provide sensitive, well-differentiated feedback.

The low-mounted steering gear transmits the steering forces via the track rods to the wheels over the shortest distance, its ratio of 16.5:1 is sporty and direct. The regulated vane-type pump, which supplies the system with hydraulic energy, always delivers only as much oil as is needed; in this way it too contributes towards high consumption efficiency. As a servotronic system, it bases the amount of assistance on road speed.

The new Audi S4 and S4 Avant are fitted with impressive cast aluminum wheels, which carry size 245/40 tires on 8J x 18 rims. As well as the standard 5 parallel-spoke wheel in the S design, an additional design is available. Furthermore, there is a choice of winter wheels in two different widths, one of which is suitable for snow chains. quattro GmbH offers three 19-inch wheels with size 255/35 tires: the 5 segment-spoke design, 7 twin-spoke design and 20-spoke design (two-piece).

The large wheels provide space for a 17-inch brake system developed for maximum performance. All four disks are ventilated, the front having a diameter of 345 millimeters (13.58 in), the rear 330 millimeters (12.99 in). An innovative concept, which dispenses with the conventional cooling ducts, ensures impressive power and stability: the two halves of the disk are connected by hundreds of small metal cubes, between which a high volume of heated air can flow in a very short time. This design also lowers the weight – here too, drivers will experience the reduction in unsprung masses in the form of enhanced driving dynamics.

The black-painted brake calipers – sporting the S4 logo at the front – are of a composite design based on the floating caliper principle. The areas subject to high loads are made of nodular cast iron; the bolted-on piston housing made of aluminum conducts the heat effectively, and the calipers are extremely rigid despite being light in weight. Compared with the predecessor model, the surface of the brake pads has increased by 25 percent at the front, and as much as 60 percent at the rear. New materials increase the amount of friction.

The brakes on the S4 and S4 Avant set new standards in terms of power and precision, not to mention accurate feedback provided to the driver. The electronic stabilization program ESP also uses high-precision hydraulic valves, which control pressure build-up with great accuracy. It intervenes at a later stage and is more subtle. The ESP can be switched off completely: the driver can deactivate the traction control function separately at a speed below 70 km/h (43.50 mph).

The equipment, data, and prices specified refer to the models offered in Germany. Subject to amendment; errors and omissions excepted.