MOTOR Magazine

A MOTOR Magazine Newsletter
Aug. 15, 2017

Contributed by Bob Chabot
Suspension Revolution

Suspension systems reconcile comfort, handling and performance

Suspension systems tend not to get much publicity, but they are one of the most crucial factors in the day-to-day enjoyment of your car. Automakers are always tweaking and refining their designs in search of one elusive ideal: A perfect ride coupled with thrilling handling and performance.

Suspension technology has evolved over the years, with innovations that moved ride, handling and performance well beyond the “driving a brick” feel of generations past. Examples include Magnetic Damping from General Motors (left), Active Curve Tilting from Mercedes-Benz (center) and Hydraulic Ride Control from the Volkswagen Group (right). (Images — General Motors, Mercedes-Benz, and Audi)

Suspension Innovations Key To Improved Ride
When General Motors first developed Magnetic Ride Control technology for its Corvette Stingray, little did the automaker expect it to become so popular that the system would be licensed to so many other OEMs. The original technology varied electric current through a ferrous fluid that allowed systems to adjust damper stiffness in response to driving conditions. But there was a lag as the ferrous particles returned to a previously relaxed compliant state. Now in its third generation, the technology has been improved by adding a second wire, which enables the fluid to be actively switched between firm and compliant states, allowing quicker adjustments to the road, even at high speeds.

When Mercedes-Benz introduced Active Curve Tilting in its 2015 S65 AMG, it provided vehicles the ability to lean into corners, like motorcyclists do. The S65 uses a lateral-acceleration sensor, forward-looking camera and air suspension to simulate banking so common on racetracks. The technology improves rider comfort by perceiving corners, then leaning into them to better manage the lateral loads on occupants. Even the seats lean into corners.

Audi debuted Hydraulic Roll Control with the cross-linked suspension in its 2015 RS 7. Conventional suspensions use steel antiroll bars to counteract body roll, but Audi’s dynamic ride control is able to send fluid to the opposite side of the car. Until the driver is pulling major G's, the system stays passive. At higher G’s, the system behaves like a fully active system — managing wheel movement, shock, vibration and more — to deliver an optimal ride.

The all-new active suspension on the Audi A8 is a fully active, electromechanical suspension system, which drives each wheel individually and adapts to the prevailing road conditions. Each wheel has an electric motor which is powered by the 48-volt main electrical system. Additional components include gears, a rotary tube together with internal titanium torsion bar and a lever which exerts up to 1,100 Nm (811.3 lb-ft) on the suspension via a coupling rod. (Video — Audi AG)

The Next Step in the Suspension Revolution
Speaking of Audi, the automaker has just taken fully active suspensions to a whole new level that maximizes comfort, ride and other dynamics. The automaker debuted the suspension on its latest A8 iteration at the Audi Summit in Barcelona in mid-July 2017, where it announced other models would soon be fitted with the innovation.

The A8 features an all-new fully active, electromechanical suspension system, enabled by a 48-volt electrical system that is fitted to all five of the A8's engine options. The 48-volt system serves as the primary electrical supply that supplies a 12-volt subsystem. The suspension system drives each wheel individually and adapts to the prevailing road conditions. Each wheel has an electric motor, which is powered by the 48-volt main electrical system. Additional components include gears, a rotary tube, together with internal titanium torsion bar and a lever capable of exerting up to 1,100 Nm (or 811.3 lb-ft) on the suspension via a coupling rod.

In addition, the A8 features an onboard Electronic Chassis Platform (ECP) module, which processes road surface information and precisely controls all of the air suspension components almost in real time. The ECP interfaces with a front camera that generates information about the road surface condition 18 times a second. This allows the system to detect bumps in the road early on and predictively adjust the active suspension to virtually eliminate any vibrations, jolts and other ride annoyances.

For example, before the car reaches a bump in the road, the preview function developed by Audi transmits the right amount of travel to the actuators and actively controls the suspension. This complex process takes just a few milliseconds. The fully active suspension specifically influences and minimizes rolling movements when cornering, and pitching movements when braking or accelerating, allowing drivers to continually keep their vehicles under control.

The innovative combination of dynamic and rear axle steering resolves the conflict of aims between agility and stability in the shape of dynamic all-wheel steering. The steering characteristics are sporty and direct while ensuring a high level of handling stability. The steering feel encompasses a wide spread from comfortable through to intense feedback. (Video — Audi AG)

In conjunction with the Audi’s Pre Sense 360˚ safety system, the active suspension takes passive safety to a new level. For instance, its innovative combination of dynamic suspension and rear axle steering resolves the conflict between agility and stability by providing the feel of dynamic all-wheel steering characteristics that are sporty and direct while ensuring a high level of handling stability.

The A8’s safety systems use sensors networked in the central driver assistance controller (zFAS) to detect risks of a collision around the car. In the event of an imminent side impact at more than 25 km/h (15.5 mph) the suspension actuators raise the body on the exposed side by up to 80 millimeters (3.1 in) within half a second. As a result, the collision is directed to the stronger areas of the vehicle, such as side sills and floor structure, reducing the side impact collision forces impacting occupants by up to 50 percent.

The result is a combination of sharper vehicle dynamics, improved safety and driver “feel-goods” when negotiating exciting roads, and increased occupant comfort when simply cruising. It’s a clear indication of how far suspensions have come.

[Editor's note: Visit for the latest diagnostic and service insights.]

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