Solution for worn VAG torsion beam rear suspension systems
Since the introduction of the Mk1 Golf, VW has used torsion beam rear suspension systems on many of its front-wheel-drive models. These are economical to manufacture and allow more room in the cabin and additional boot space – vital assets in the competitive small and medium car markets. And, even though cars using the Mk5 and Mk6 Golf platforms have adopted more sophisticated multi-link rear suspension systems, VAG is still using the beam axle on cars based on the Polo platform.
The torsion bar beam axle design features a system that incorporates two trailing arms linked with a torsion tube or ‘’beam’’. The weight of the vehicle bears directly through the springs and onto the wheel bearings at the end - or near the end - of the trailing arms. The roll-control of the vehicle is then achieved by the beam twisting in order to limit the independent movement of the trailing arms without the need for a rear anti-roll bar.
The system is mounted to the chassis at two fixed points through a uniquely designed rubber-to-metal pivot bushing. This joint is responsible for locating the axle and helps control the rear suspension geometry, whilst allowing a small amount of passive rear wheel steer. The importance of the role played by this mounting increases when seeking performance improvements, such as fitting larger wheels and tyres, firmer springs and dampers, or aftermarket anti-roll bars.
Degradation of the beam axle pivot bushing will consequently lead to excessive or incorrect movement in the mounting, which in turn may lead to body roll, erratic rear-steer and potentially unbalanced handling. At best, a worn or tired bush will increase the feeling of vagueness and reduced control in the rear suspension.
It is therefore important these bushings are inspected at regular intervals to check for bonding failure between the rubber, the outer shells and the inner metal tubes, as well as for cracks appearing in the rubber – and not necessarily only at MOT time. Both symptoms will allow excessive flex and torsion beam movement, which can lead to unpredictable and potentially dangerous handling and erratic behaviour.
VAG has tried a range of different ideas in an effort to achieve optimum performance, such as using alloy tubes and composite shells for the bushes. However, by using carefully designed polyurethane with its unique properties, SuperPro engineers have been able to develop a single solution for general repair and to achieve a better performance. In particular, the well-proven Mk4 Golf bushes and the similar kit, for current Polo 6R-based cars, are good examples of how a SuperPro bush can overcome the inherent issues.
Because of the unique design and materials used by SuperPro, its replacement bushes enable the torsion beam to locate firmly enough to provide consistent geometry and control, whilst still allow a limited amount of passive rear-steer - perfect for normal driving and performance applications. In addition, free pivoting movement in the vertical plane alleviates unwelcome levels of noise, vibration and harshness.
- VW Golf Mk4, two-wheel-drive and VW Polo 9N-based applications (part number: SPF2481K)
- VW Polo 6R-based applications (part number: SPF3616K)
The two-piece SuperPro design allows easy fitment with installation of the new bush possible without the use of a press – and potentially without completely removing the axle from the car.