The chassis also demonstrates the technological expertise that Audi is investing in the A4 family. All models, from the A4 allroad quattro to the S4, turn spontaneously into corners and remain stable with virtually neutral handling at the very high limit. The composed straight-line tracking and high rolling comfort round out the sporty, balanced impression. The A4 models have a wide track. It measures 1,564 millimeters (5.13 ft) up front in the Sedan and Avant and 1,583 millimeters (5.19 ft) in the allroad quattro. At the rear these figures are 1,551 millimeters (5.09 ft) and 1,574 millimeters (5.16 ft), respectively.
To reduce the unsprung masses, numerous front suspension components are made of aluminum. Audi uses the lightweight material for the integral frame for the engine and axle, which is firmly bolted to the front section of the car for increased rigidity; for the bearing mount that links the upper suspension control arms with the body; for the pivot bearing; and for the five control arms per wheel. The five-link design can handle longitudinal and lateral forces separately. Their bearings are stiff in the lateral direction, fostering sporty precision; on the other hand, the bearings are comfortably pliable in the longitudinal direction. A tubular anti-roll bar also cuts down on weight.
One innovation in the A4 model series is the highly efficient electromechanical power steering, which adapts its boost to the driven speed. The electric motor integrated into the steering gear consumes no energy when driving straight ahead, which depending on the engine lowers fuel consumption by as much as 0.3 liters per 100 km (7 grams CO2 per km [11.27 g/mile]). The concentric arrangement of the steering rack and the servo drive minimizes the dimensions of the steering gear.
The new electromechanical power steering works closely together with the optional Audi active lane assist system. The steering ratio of 15.9:1 is sporty and direct, and the steering gear transfers the input directly to the wheels. Feedback from the road is spontaneous and responsive: traction forces and disruptive forces are practically imperceptible. The Audi A4 has a turning circle of approximately 11.5 meters (37.73 ft).
The rear axle is a track-controlled trapezoidal-link construction that combines low space requirements with excellent driving and comfort qualities. A flexurally and torsionally rigid steel subframe connected to the body via hydraulic bearings constitutes the ultra-strong backbone. Two hollow trapezoidal links, the wheel carriers, the overhead control arms and the tie rods are made of aluminum; a lightweight section serves as an anti-roll bar.
The springs are supported directly by the wheel carriers and are spatially separately from the twin-tube, gas-pressurized shock absorbers to facilitate particularly calibrated response. The shock-absorber tuning and the arrangement of the rear trailing arms are more finely tuned than ever before – which enhances not only the ease but also the sporty precision of handling.
A sport suspension is available as an option for the Sedan and the Avant; it is standard with the Ambition line. Another option is the S line sport suspension, which lowers the body by 30 millimeters (1.18 in). The suspension is also available with adaptive damping control. The CDC (continuous damping control) shock absorbers include electromagnetically actuated valves that control the flow of hydraulic fluid between the shock absorber tubes.
This makes a sporty driving style possible as well as enabling a comfort-oriented configuration, which may be preferred on long highway journeys, for example. The central control unit computes the flow for each shock absorber separately every few milliseconds, taking into consideration the road conditions, the driver’s style and the mode chosen in Audi drive select.
High-end technology: Audi drive select
Audi drive select is one of the high-end features in the A4 model series. In the basic package, it enables the driver to modify the characteristic of the accelerator, the shift points of the automatic transmission and the power steering boost at the push of a button. Additional components can be integrated into the system as options, including the sport differential (for the six-cylinder engines), the damper control, the dynamic steering and the conventional cruise control system or adaptive cruise control.
Audi drive select offers the driver the choice between comfort, auto, dynamic and efficiency modes. The latter mode is new. It also influences the air conditioning and the optional adaptive cruise control or the conventional cruise control system. If the vehicle is equipped with the MMI navigation system, an additional mode, individual, is also included. It allows the driver to specify, within certain limits, their very own profile of preferred settings.
The dynamic steering, which is also electromechanical, uses a superposition gear so that the steering ratio can be varied by nearly 100 percent. Under city-driving conditions, the ratio is very direct; at high speeds, an indirect steering ratio supports smooth straight-line stability. The system supports the driver when cornering at the handling limits, if necessary, reducing both oversteer and understeer by means of load changes.
Elegant: the wheels
The Audi A4 rolls off the production line on elegant wheels. The 1.8 TFSI and 2.0 TDI Attraction with 88 kW (120 hp) have steel wheels; all other variants have alloy wheels. The four-cylinder models in the Attraction and Ambiente trim lines come with 16-inch wheels shod with 225/55-series tires. The sporty Ambition line and the V6 models come standard with 17-inch wheels and 225/50-series tires.
A4 customers can choose from a wide selection of optional wheels. All told there are 18 variants plus another four independent designs for the A4 allroad quattro. Topping the range, which includes four new designs, are exclusive solutions such as the 20-spoke design and the titanium-look, five-arm rotor design. Diameters are as high as 19 inches with 255/35-series tires. The four winter wheels range from 16 to 18 inches in diameter. An indirect tire pressure indicator and a repair kit are standard on all models; a compact spare wheel is optional. Some tires have run-flat properties.
Powerful brakes are located behind the large wheels. Depending on the engine, the discs measure up to 320 millimeters (12.60 in) up front and 300 millimeters (11.81 in) in the back. The two disc halves of the vented front brakes are connected by hundreds of tiny metal cubes for excellent heat dissipation. The brake pads achieve high friction rates.
A4 models with the most powerful engines feature composite brake calipers. The aluminum piston housing dissipates the heat very well. The calipers are lightweight yet extremely rigid; the brake discs and cover plates are also very light. In conjunction with the electromechanical steering, the electronic stabilization program (ESP) aids drivers with braking and countersteering whenever both tires on one side encounter a slippery surface.
ESP with electronic limited slip differential is standard for all front-wheel drive versions of the A4 series. The software solution is active during fast cornering. If the control unit detects that the inside front wheel is at risk of spinning, the control unit will moderately brake that wheel.
The excess torque flows through the differential to the outside wheel, while the difference between the drive forces causes the car to turn very slightly into the corner. The A4 corners precisely, agilely, stably and virtually neutrally.
The Audi A4 allroad quattro features a special technology called Offroad Detection (ORD). This system detects the properties of the surface and adjusts the control characteristic appropriately. The ESP improves propulsion when accelerating on loose surfaces by tolerating more slip.
The equipment and data specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.