Vauxhall/Opel reveals details of new Astra´s chassis

The upcoming Vauxhall/Opel Astra, which will debut at the Frankfurt Motor Show in September, will not only feature a longer wheelbase and wider track for improved stability and ride comfort, but also a cleverly positioned Watts link rear suspension system that its makers hope will offer drivers class-leading handling and ride comfort. The FlexRide adaptive damping system will also be available on most Astra models, and its Sport mode will include a customization menu, where the driver can de-select the damper and steering-assistance elements.

The new Astra’s front and rear tracks have been increased by 56mm and 70mm respectively, while its wheelbase has been increased by 71mm, the cumulative effect being improved handling and ride quality, as well as more space and comfort for occupants. A core body structure that’s stiffer than that of the outgoing car enhances the new Astra’s ride and handling still further, while also reducing noise and vibration inside the cabin.

The Astra’s new suspension layout combines MacPherson strut front suspension with a newly developed compound crank rear axle with a Watts link. Project engineers say that this setup has many advantages over a multilink design, including improved packaging, greater wheel camber stiffness and less lower suspension friction. It also creates less camber loss due to body roll, while the Watts link ensures that lateral stability is maintained.

The torsion beam of the compound crank axle is attached between the trailing links, about half way between the axle bush and the rear wheel. The open, U-shaped profile between the attachment points has now been lengthened and the wall thickness generally increased to provide more roll stiffness. In addition, beams with different wall thicknesses are fitted to give the required roll-steer characteristics.

The Watts link is carried on a small cross-member attached to the underside of the car, just behind the rear wheel centerline. It comprises a short, pivoting center link with a ball joint at each end, to which the lateral links from the wheels are bolted.

The setup has been designed to ensure excellent straightline stability, but during cornering it minimizes lateral deflection in the same way a modern multilink system would do. In addition, the Watts link reduces axle bush loads to allow softer bushings, which further isolate occupants from road noise and vibration.

The front MacPherson struts incorporate dual-path top mounts that separate spring and damper forces. To reduce unsprung weight and assist weight distribution, the knuckle and the lower control arm are made from aluminum and the anti-roll bar from hollow section steel.

The L-shaped control arm is attached through two bushings to the front subframe. The front bush has been made particularly stiff to optimize handling, while that at the rear is a radial-loaded hydro-bush. The suspension geometry and the tuning of the bushes are designed to provide both lateral stiffness and longitudinal compliance to benefit ride comfort and handling. The rearmost bush of the L-arm is also hydraulically damped for excellent road isolation, helping to prevent vibration transmission into the car’s cabin.

Click here to ride with a mystery guest as he test-drives the Astra at Millbrook