The Audi R8: The Suspension
The precision sports car
Sporty performance or everyday suitability? Dynamic or comfortable? Such issues are academic in the case of the Audi R8. It is equally capable of race-standard agility and pleasurably relaxed driving for lengthy journeys. Thanks to its elaborate suspension technology, Audi’s new masterpiece provides an astonishing level of comfort as well as being supremely sporty.
But the most important term for describing the driving feel in the Audi R8 is precision that thrilling spontaneity with which this sports car instantly acts upon every movement of the steering wheel and every request for acceleration or braking. The R8 may be responding to the steering wheel, but it almost appears to be responding to the driver’s thoughts.
The Audi R8 is ultimately an excellently executed mid-engine sports car. Even in theory, this concept has compelling advantages: unlike a car with its engine at the front or rear, in this case the engine is located very close to the car’s vertical axis. The weight is concentrated around the centre of the car and the mass moment of inertia when it spontaneously changes direction is much lower.
,b>Exceptionally high driving safety
This responsiveness lends the R8 a high degree of active safety: a car that steers and brakes well can drive away from hazards faster than an unresponsive car. On the Audi R8, this agility above all goes hand in hand with exceptional driving safety: together with the neutral self-steering behaviour and the wheelbase of 2.65 metres, which is long for a sports car, the excellent quattro drive provides particularly good directional stability.
And before the extremely high limits of handling can be exceeded, the painstakingly optimised ESP stabilisation system intervenes. It offers two levels of protection: the standard mode, which fully preserves both the agility of the R8 and its reserve safety, and the sport mode, which permits greater transverse dynamics for very sporty driving. And those who wish to push their R8 to the limit on a racetrack can switch off ESP, complete with its traction control feature.
Precision with a crafted character
This precision of course stems from a whole raft of skilful engineering solutions. An essential basis for a precise driving feel is a high-rigidity body structure that does not exhibit any tolerances or waywardness even under extreme loads. The Audi Space Frame of high-strength aluminium, with its cage-like structure, is virtually without par at providing this rigidity.
The body production shop in Neckarsulm supplies sheer precision as the basis: after the structure has been welded and riveted, all 52 connecting points for the running gear and steering are machined in a single pass. An automatic station mills, drills and cuts threads precise to one-tenth of a millimetre. This ensures that the suspension geometry planned by the engineers is realised with precision on every production car. An automatic measuring system in the production shop scans 220 measuring points on every body with its 95 laser sensors to verify this.
High-tech in every suspension mount
The basic suspension layout, with double wishbones at both the front and rear, reflects the concept used by almost every racing car right up to Formula 1 level. To reduce the unsprung weight, virtually all suspension components are made from forged aluminium. Particular attention has been devoted to the comprehensively new rubber-metal mounts that connect all axle components to the space frame. These mounts look simple, but are in actual fact individually coordinated high-tech elements. They transfer the transverse forces with precision, while filtering out undesirable vibrations.
A new double wishbone structure with an additional track rod is used at the rear. It permits a defined toe characteristic under load. This makes a huge contribution towards the ease with which this high-performance car can be controlled along with the grip-optimised damper settings that avoid wheel load fluctuations. By separating longitudinal and transverse forces, it has moreover proved possible to combine sporty precision with very comfortable suspension and acoustic comfort.
Ride comfort, magnetically controlled
A particularly innovative damping technology is available for the R8 as an alternative to the standard gas-filled shock absorbers: Audi magnetic ride adapts the damping characteristic to the profile of the road and the driver’s style within milliseconds. This consequently resolves the conflict between driving dynamics and comfort without countenancing any compromises.
The pistons of these shock absorbers do not contain conventional oil, but a magneto-rheological fluid a synthetic hydrocarbon oil in which microscopically small magnetic particles are enclosed. When an electrical voltage is applied to a coil, a magnetic field is created, causing the alignment of the particles to change. They arrange themselves transversely to the direction of flow of the oil, thus inhibiting its flow through the piston channels. The damper becomes instantaneously firmer.
The advantage of this technology is that damper adjustment responds much faster to the commands from the electronic control unit than previous systems with an adjustable valve. The control unit is supplied by complex sensing technology and constantly monitors the optimum values for each wheel. If the driver for instance enters a bend, the damping force for the wheel on the outer arc of the bend is increased. This reduces body roll even further and the car responds with even greater spontaneity.
Depending on the driving situation and personal preferences the driver can choose between the standard and sport modes: heightened ride comfort for long distances and poor roads, or overt dynamism for taking every bend in the road with relish.
Steering with sensitivity
The steering, operating precisely and supplying sensitive feedback, provides the driver with direct feedback from the road surface. With a steering ratio of 17.3:1, the hydraulically assisted rack-and-pinion steering operates very directly. An important aspect of the R8’s everyday suitability is the turning circle of 11.8 metres, which is small for a sports car.
This makes the R8 astonishingly manoeuvrable, even though the tyres inside its wheel arches are of mammoth proportions. In the basic specification, 18-inch cast aluminium wheels fitted with 235 mm tyres at the front and 285 mm tyres at the rear provide the necessary grip. 19-inch wheels are available as an option, in which case they are equipped with 295 mm tyres at the rear. The R8 is naturally suitable for driving all the year round, not least thanks to its quattro drive: both 18-inch and 19-inch winter wheels are available.
Braked by 24 pistons
The requirements that the brake system needs to meet on a sports car are very varied: it must ultimately withstand the extreme loads of a racetrack, but also handle stop-and-go driving in urban traffic with ease. Two fixed-caliper brakes painted black, each with eight pistons, are fitted to the front wheels to provide the necessary braking performance, complemented by four pistons on each wheel brake at the rear.
There are particularly elaborate studded composite brake discs with the impressive diameters of 380 mm at the front and 356 mm at the rear. They comprise the friction ring and an aluminium central element connecting the stainless steel studs. This arrangement means on the one hand that thermal expansion of the disc when subjected to high loads does not affect the central element. On the other hand, the use of aluminium cuts the weight of each disc by about two kilograms. And weight-watching is always a key issue for a sports car.
Ceramic brakes with extreme reserves
For even better performance coupled with a further reduction in weight and longer service life, there are the optional ceramic brakes. In this instance the discs are made from carbon fibre reinforced ceramic, a material that has repeatedly proven its worth in the aviation and aerospace sectors. The basis is very hard, frictionally resistant silicon carbide, with its diamond-like crystalline structure. Embedded in it are high-strength carbon fibres that absorb the stresses that occur in the material. The intricate geometry of cooling ducts in the ventilated discs prevents extremely high temperatures. The ceramic brake disc ring is bolted via ten sprung elements to a stainless steel central element that acts as the connection with the wheel’s hub.
The ceramic brakes are identifiable at a glance by the anthracite-coloured special six-piston monobloc aluminium calipers and the fixed calipers at the rear. The advantages of the ceramic brakes include a further reduction in weight of around 20 kilograms, which in this case improves the handling characteristics and comfort response. The high abrasion resistance permits an operating life of up to 300,000 kilometres. Their trump card however is their insusceptibility to very high loads.
Even when in operation on the racetrack, for example, the ceramic brakes always maintain their full reserve performance. The ceramic brakes are expected to become available for the R8 from the end of 2007.
When it comes to reliability and durability, the R8 must of course satisfy the renowned high standards of the Audi brand as effectively as any other product. And more: they were put through the ultimate trial of several endurance runs covering more than 10,000 kilometres on the racetrack, with DTM drivers behind the wheel. The circuits driven included the North Loop of the Nürburg Ring, where every single kilometre represents a multiple of the loads encountered on ordinary roads.
The equipment, data and prices stated here refer to the model range offered for sale in Germany. Subject to amendment; errors and omissions excepted.