Press Release
Running gear
The new A4’s dynamic suspension combines sporty precision with high stability and supremely confident road behaviour. It is a totally new design, with many components made from aluminium in order to reduce unsprung weight. Two technological breakthroughs make the driving experience even more fascinating: adaptive shock absorber control and Audi dynamic steering.
The Audi dynamic steering system alters its effective ratio according to road speed, and helps to keep the new A4 stable when the handling limits are approached by making slight but extremely rapid steering corrections. The adaptive shock absorber control maintains optimal tyre contact with the road, for safety allied to dynamism in just about every situation, and so that even the enthusiastic driver can be sure that maximum safety is always available.
Interchanging the differential and the clutch has enabled the front axle to be moved forward by 154 millimetres. This change, aided by moving the car’s battery to the boot, helps to achieve ideal weight distribution.
With its wide track –1564 mm at the front, 1551 mm at the rear – the A4 suggests its dynamic power even at a standstill. To drive it is to experience the sportiest car in the midsize category: agile, effortless to handle and safe at all times. With its almost neutral steering response, the new A4 can be cornered at high speeds.
Strong structural members – rapid build-up of forces
The front axle pivot bearings and the five links that locate each front wheel are made of aluminium. At the front of the A4, the engine and suspension support beam is also made of aluminium, and bolted rigidly to the body.
The steering gear is located low down and well forward, with the track rod transmitting steering movements directly to the wheels. Rack and pinion steering provides well-defined, sensitive feedback from the road but transmits in effect no undesirable jolts or shake. The steering ratio of 16.1:1 is sporty and direct, but never nervous in its response. The controlled-output pump only delivers the amount of power steering oil actually needed; this lowers fuel consumption by about 0.1 l/100 km. Cars with V6 engines are equipped as standard with power steering that varies the degree of assistance according to road speed.
The development engineers based the design of the rear suspension on the controlled toe-angle principle with trapezoidal links used for the larger A6 and A8 model lines; this is a space-saving layout that combines sporty handling with a high level of ride comfort.
Applying the lightweight construction principle, the steel axle beam is attached to the body by four rubber bushings; these are very rigid laterally to ensure dynamic handling, but softer longitudinally for greater vertical and lengthwise compliance. The trapezoidal links, wheel carriers, upper wishbones and track rods are all made of aluminium. The well-proven solution comprising separate spring and shock absorber mountings, and in particular the new spring connection points at the wheel carriers, ensure good initial suspension response.
Versions of the new A4 with engine outputs up to 118 kW (160 bhp) run on pressed-steel wheels with full-size wheel covers and 205/60 R16 tyres. Cars with more powerful engines have elegant alloy wheels and 225/55 R16 tyres. Optional extras are also available from quattro GmbH: 18-inch wheels with 245/40 tyres and also 19-inch wheels. 8 J x 17 wheels can be obtained with run-flat tyres. Standard equipment on cars with a V6 engine is a tyre pressure monitoring display that operates extremely accurately and reliably.
Powerful stopping too – the brake system
Behind the car’s big wheels are brakes with 314 mm diameter front and 300 mm rear discs; the front discs are internally ventilated. The high-performance brake pads, a new development, now cover 20 percent more rubbed area. The front brakes on V6-engined cars are even larger, with 320 mm discs and composite spheroidal-graphite and aluminium callipers. In every version of the A4, the brake pedal has a firm, precise action, and thanks to accurate feedback the driver can control the brake application effectively without applying excessive pressure.
The latest generation of ESP stabilisation system adds to the operating refinement of the brake system. New hydraulic valves build up pressure with exceptional accuracy, and the regulating action takes place without judder. At speeds below 70 km/h, the driver can disconnect certain anti-slip functions by pressing a button briefly. The wheels can then spin, but this can be beneficial in certain circumstances, for instance when driving on snow.
ESP in the new A4 has a number of additional functions – it can for instance stabilise a trailer if it begins to snake, dry the brake discs in wet weather and activate the hazard warning flashers if a panic brake application is made.
Audi drive select – up to four different cars in one
Those who drive the A4 hard and enthusiastically can choose between two sports suspension settings, or alternatively rely on an innovative technology – the innovative system known as Audi drive select. This is available in various stages, which influence an increasing number of technical components and functions on the car: accelerator pedal response, tiptronic shift points, power steering assistance, the steering ratio and the action of the electronically adjustable shock absorbers – another new feature.
The driver can select the comfort, auto or dynamic modes at switches on the centre console. If the A4 is equipped with the MMI control system, a fourth mode, “Individual”, is available; this enables an individual profile of 24 settings to be configured. Audi drive select transforms a single A4 into up to four different cars – a range of driving pleasure, dynamism and ride comfort that is unmatched in the midsize car category.
As fast as a professional rally driver –Audi dynamic steering
The new A4 features yet another pioneering technological development: Audi dynamic steering. Its key element is a superimposed gear system that alters the overall ratio according to road speed and the chosen Audi drive select setting. This concentric-shaft steering gear is extremely compact and light in weight; it has a precise action free from any slack. It was first developed for use in robots and for space travel applications; the expedition vehicles on which it was installed have already traversed the surface of the moon and Mars.
Audi dynamic steering makes the steering ratio more direct at low speeds, with a higher level of power assistance. This renders the steering extremely light when manoeuvring, and only two turns of the wheel are needed from lock to lock. As the car’s speed increases, however, the steering ratio becomes gradually less direct and in parallel with this the amount of power assistance is reduced. At high motorway speeds the A4 can therefore be driven smoothly and has excellent straight-line stability.
Audi’s high-tech steering can do even more. It is closely networked with the ESP and therefore receives precise information about the car’s attitude as the handling limit is approached. If the A4 threatens to oversteer, for instance after an abrupt avoidance manoeuvre, the steering performs slight corrective impulses in the direction needed to reduce this tendency. Such corrective action takes place faster than even an experienced rally driver could react. This rapid response means that brake applications are often not needed, so that the car continues its journey more smoothly and dynamically.
The system also takes action if the car understeers: it selects a more indirect steering ratio for a short time, the aim being to prevent the driver from turning the steering beyond the point at which the tyres still have plenty of road grip. With these capabilities, Audi dynamic steering represents leading-edge technology in this car market segment.
The optional-extra damping control permits individual suspension settings to be chosen. These are based on the lowered sports suspension. Continuously adjustable hydraulic shock absorbers permit the damping characteristic to be varied individually at each wheel. This means optimal contact between the tyre and the road in almost every situation, for greater safety and more dynamic road behaviour.
