The Torsen center differential combined with computer controlled braked biased traction control (ESP) provides superior grip in all driving conditions. High performance driving on wet/dry roads is excellent, and switching to a seasonal winter tire set gives predictable traction for snow and ice control.
The RS6 was only available with Audi's Torsen-based quattro permanent all-wheel drive system. The heart of it all is the Torsen T-2 dynamic "automatic torque biasing" center differential. The torque from the engine is first routed from the gearbox rear output shaft to the Torsen centre diff, and then automatically divided and apportioned between the front and rear axles. When one or both wheels slip on a given axle, power is then mechanically shifted to the front or rear axle that is getting the most traction. This mechanical geared Torsen system is constantly working to achieve maximum traction on all surfaces. The natural balance of power with complete traction is 40% to the front and 60% to the rear.
The front and rear axle differentials are a conventional "open" type, but mimic an Electronic Differential Lock (EDL). EDL is an integrated additional function of the Bosch Electronic Stability Program (ESP) system, and works by monitoring and comparing the individual wheel speeds across an axle, and then applying brake an individual wheel which is sensed to have lost traction (sensor reported spinning/slipping at a higher rate than the other); thus transferring torque across the axle to the wheel which does have grip. Anti-Slip Regulation (ASR), more commonly known as the computer/sensor controlled traction control system, completes the Bosch ESP-related system. This computer controlled system can be toggled on or off by a button on the dash. Having the option to turn off the ESP/ASR allows for driver focused spirited driving that puts the driver in complete control, while still having the mechanical gear driven Torsen Quattro system to balance power and maintain traction.
DRC Suspension and Modifications
Utilizing the same fully independent four-link front suspension and double wishbone rear as the related A6 and S6, the RS6 was lowered by 20 millimetres and given a 30% stiffer spring rate and 40% increased compression damping. The RS6 also used Audi's "Dynamic Ride Control" (DRC) system. The DRC system is mainly mechanical, and uses a pump to provide additional pressure to individual struts (shock absorbers) under more load. The system can adjust the stiffness at each individual damper constantly, to maintain both a comfortable ride on straight roads, and high level of poise and grip when cornering. Its main drawback however is that the DRC dampers have been known to fail (leaking fluid from the cross-linked circuits), which hurt the handling and ride quality of the vehicle. Some owners have reported needing multiple replacements of faulty DRC units, while others have had success with the second generation version when installed and cared for correctly.
Many drivers have opted to replace the system with simpler and more reliable aftermarket coilover suspension that allows for height and performance tuning. Another cost effective and suspension update is to just replace the DRC struts with Koni Yelllow Sport struts, while still utilizing the original springs. The handling is firm yet not too harsh, and the height of the body is reduced about 3/4"; increasing both performance and looks. The other common suspension upgrade is the Hotchkis sway bar for both front and rear. These greatly reduce body roll and help to reduce understeer.