Automakers have been fighting the effects of physics since the very first car rolled off the assembly line. We’ve come a long way in our command of a car’s behavior on the road, but one of the biggest fights has to do with how a car behaves going around corners. Physics says that a car should lean when turning. The tires grip the road, the suspension on the outside of the car compresses, and the body leans to the outside. Roll-stabilizing systems aim to keep that listing motion under control. Conventional anti-roll bars are steel torsion springs that connect the left and right suspension members – transferring force from the outside suspension to the inside while cornering, which in turn reduces body roll.
The biggest issue with conventional anti-roll bars is that they effectively link both sides of the car together, so a single-wheel bump encountered while driving straight affects both sides of the car, reducing ride quality.
Innovative new roll-stabilization systems are using active and passive methods to strike a balance between cornering control and ride quality.
These systems use sensors and control units to actively resist roll during turns and provide a comfortable ride when travelling in a straight line.
Split Sway Bar with Actuator
Perhaps the most popular way to actively control body roll is through a sway bar that has been cut in two and coupled together with an electric motor or hydraulic actuator between the two halves. This allows torque to be applied to each side independently, and can even completely disconnect the sway bar in off-road applications. This is popular in many BMW, Bentley, Lexus, Mercedes-Benz, and Porsche SUV models.
Active End Links
This system is found on the Porsche 911 and is known as Porsche Dynamic Chassis Control. It replaces the traditional end links that connect the sway bar to the suspension with hydraulic actuators. These actuators suppress body roll by lengthening or shortening the end links during cornering, thus loading or unloading the sway bar as needed.
Audi AI Active Suspension
This electrically-driven system replaces the sway bar on the 2019 Audi A8 completely. Instead, there is a 2.7-horsepower electric motor at each corner of the car that is connected to the suspension via a small torsion bar that works in conjunction with the car’s factory air springs. It controls body roll, minimizes bump intrusion into the cabin, and it can reduce acceleration or braking-induced pitch.
McLaren’s Hydraulically Linked Dampers
This ingenious system cooked up by the guys over at McLaren links the compression chambers of the right-side shock absorbers with the rebound chambers of the left-side and vice versa. As the suspension compresses on one side, oil pressure increases within the system and resists body roll. This allows McLaren to adjust how aggressive the system works by stepping the pressures up or down based on the driving mode selected. This system is found on the P1, Senna, 650S, 675LT, and 720S.