The Audi S3: Chassis

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August 28, 2006

Source: Audi AG

The premium compact A3 already features a very mature chassis design, all components of which have undergone some decisive improvements compared with the previous model. The engineers have refined it even further for use in the top sports model – the S sports suspension exhibits the qualities that one would expect of a sports car.

The springs and dampers are correspondingly firmer, in line with the car’s ultra-sporty character, and the body is slung 25 mm lower. At 1,522 mm at the front and 1,506 mm at the rear, the new S3 now has a wider track. Imposing 18-inch wheels made from cast aluminium with size 225/40 tyres are standard.
quattro GmbH can supply special designs of 18-inch wheels on request.

The front axle: even more lightweight aluminium components

The front suspension uses a classic design principle – a McPherson structure with spring struts, triangular lower wishbones and an anti-roll bar. The aluminium subframe is bolted to the longitudinal member, keeping the forward structure very rigid. The wishbone consoles are equally of aluminium. On the S3, the pivot bearing and the triangulated wishbone are likewise made from aluminium – this optimises the weight distribution between the two axles and benefits the unsprung weights, which are important for the handling characteristics and ride comfort.

The front-axle bearings have been uprated compared with the A3, for an even more spontaneous steering response and even more precise handling. The electromechanical steering familiar from the A3 has been matched to the S sports suspension, with the result that it gives the driver optimum feedback from the road in every situation. It remains largely unsusceptible to feedback from the drivetrain.

Unlike a hydraulic assembly, it only uses energy whenever the steering is actually being turned. The S3 reacts to all steering commands with high precision and spontaneity. The self-steering behaviour is neutral right up to the very high handling limit, which signals itself to the driver through slight understeering.

The rear axle: three wishbones and one trailing link.

The rear axle, notable for its excellent handling from the A3, has remained unchanged in terms of its basic components; its springs and dampers have been adjusted to settings typical of a sports car. The four-link structure comprises two lower wishbones, one upper wishbone and one trailing link. All links are made from high-strength steel grades.

The three wishbones are connected to the aluminium subframe by means of relatively rigid mounts, in the interests of optimum directional stability; the subframe, which also supports the anti-roll bar and the quattro final drive, is bolted to the floor assembly.

The coil springs and gas-filled shock absorbers are arranged separately, permitting a larger through-loading width in the luggage compartment.

Benefit: soft longitudinal response

The elaborate structure combines a whole raft of advantages. It is lightweight and compact, and can absorb the longitudinal and lateral forces acting on it independently. The advantage of this is that each bearing can be tuned precisely depending on its function. On the one hand, the engineers have achieved a very high degree of transverse rigidity for optimum driving dynamics, while on the other hand the trailing links are set up soft enough to provide outstanding ride comfort.

The brake system is closely in tune with the talents of the Audi S3. Four large-dimension, ventilated disc brakes provide safe, dependable deceleration. The front discs measure no less than 345 mm in diameter. The black-painted callipers, sporting the S3 emblem, house sports brake pads that combine high performance with incisive response.

The brake management: ESP and EDL

A brake assist system that automatically builds up full pressure in the system in emergency situations is part of the standard specification, as is the ESP electronic stabilisation program. It integrates such features as the electronic differential lock EDL, which applies the brakes to enhance traction when accelerating whenever the grip beneath the wheels is inconsistent. ESP intervenes subtly and precisely. If the driver presses the brakes hard, he experiences the pedal as direct, taut and progressive, with short free travel.

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