Thursday, November 5, 2009

2011 Mercedes-Benz SLS AMG Gullwing In-Depth: Chassis And Braking System

2011 Mercedes-Benz SLS AMG Gullwing Chassis and Braking

The motor sports derived technology to be found everywhere in the powertrain of the Mercedes-Benz SLS AMG is also evident in the suspension and braking system. The aluminium suspension with double-wishbone axles is designed for uncompromising lightweight construction and outstanding handling dynamics. On request the AMG high-performance braking system is also available in a newly developed, highly stress-resistant ceramic version, with composite brake discs all-round.

The commitment of Mercedes-Benz and AMGto building a highly desirable super sports car that combines consummate racetrack performance with hallmark Mercedes long-distance comfort has given rise to an ingenious suspension layout. All four wheels are located on double wishbones with a track rod, a technology that has proven itself in motor racing right through to Formula 1. With a double-wishbone axle, the wheel location and suspension functions remain separate; the spring/damper struts are supported on the lower wishbone. The double-wishbone concept with its high camber and track rigidity positively locates the wheel with minimal elastic movements, providing the driver with an optimum sense of road contact when driving at the limits.

The suspension setup of the SLS AMG ensures optimum, low body roll and a stiff basic configuration with good suspension comfort. A Performance suspension is also available on request: compared to the standard suspension, the spring rate and damping are respectively around 10 percent and 30 percent stiffer. The Performance suspension is conducive to even more agility and lateral dynamics, as well as a further reduction in body roll when driving at high speeds – for example on the racetrack.

Long wheelbase and wide track

The long wheelbase of 2680 millimetres not only results in outstanding straight-line stability but also low wheel load shifts, significantly reducing the vehicle's tendency to dive and squat when braking and accelerating. The broad track width – front 1682, rear 1653 millimetres – ensures lower shifts in the wheel loads from the inner to the outer wheel when cornering, enabling the tyres to retain more grip. The large caster angle of 11.6 degrees significantly increases negative wheel camber on the outer wheel when cornering, and also improves tyre grip – this also ensures outstanding stability when braking heavily while cornering.

Weight-optimised "Flow Forming" AMG light-alloy wheels

The weight-optimised axle design is complemented with AMG light-alloy wheels produced by the new "flow forming" process. During this production process, hot forming in the area of the rim base makes for a denser material structure, thereby improving long-term durability. This also means that lower wall thicknesses can be used. The weight saving of around 1.1 kilograms per wheel compared to conventional light-alloy wheels reduces the unsprung masses, further improving the handling dynamics and suspension comfort.

The AMG light-alloy wheels in size 9.5 x 19 inches at the front and 11.0 x 20 inches at the rear are shod with 265/35 R 19 size tyres at the front and 295/30 R 20 at the rear. Three variants are available: AMGlight-alloy wheels in a 7-spoke design or a 5-twin-spoke design, or alternatively low-weight forged wheels in a 10-spoke design. With an approx. 14-percent lower weight than the "Flow Forming" wheels, these reduce the unsprung masses even further. The weight saving per wheel is 1.8 kilograms. Tyres developed exclusively for the SLS AMG ensure top performance and excellent grip.

A tyre pressure control system which continuously monitors the pressure in all four tyres is standard equipment, with the data for each wheel shown in the display. During a journey, four wheel sensors on the insides of the light-alloy wheels send out continuous radio signals with information about the air pressure, tyre temperature and direction of rotation. A control unit evaluates the data and informs the driver in the event of a deviation from the nominal values. In this case the display shows the message "Check tyres!", or in case of a sudden pressure loss "Attention. Tyredefect!". A yellow warning lamp also lights up in the instrument cluster.

Power-assisted rack-and-pinion steering for direct feedback

With a constant mechanical steering ratio of 13.6:1, the rack-and-pinion steering of the SLS AMGprovides direct feedback and meets the high expectations for a super sports car. The servo assistance is speed-sensitive, improving the feedback to the driver as the speed increases – an indispensable factor when driving straight ahead at high speed. Perfect linear transfer of the steering angles is made possible by the constant velocity joint integrated into the steering system. The chosen geometry also provides plenty of scope for the performance-enhancing headers in the sports exhaust system.

Installing the steering gear on the subframe in front of the engine allows a particularly low engine position. The subframe is of high-strength steel, and is rigidly bolted to the side members. It not only optimises steering precision, but is also a key component in the front-end crash structure.

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