INSTALLING SHOCK ABSORBERS FREE FROM DISTORTION

When a vehicle’s shocks or dampers need to be changed, it’s essential for the part to be installed free of distortion

Improper assembly can lead to warping, resulting in a reduction in service life of shock absorbers, as well as serious component damage.
For best practice, ZF Aftermarket has described what to pay attention to during inspection and installation of shock absorbers; and explained the causes as well as effects on the chassis component technology and suggests preventative solutions.
According to ZF Aftermarket, there are two main reasons for shock absorber distortion:
1. The shock absorbers’ mounting points are displaced, meaning they are no longer flush. This can also cause the piston rod to bend.
2. A lack of care during the installation process.
If the shock absorber has been installed with a distortion, this may affect the vehicle’s performance. When a drop in performance is reported, the workshop should check for worn-down seals.
Due to the distortion, one side of the chromium plating on the piston rod surface will press against the guide and sealing unit with each stroke – ultimately wearing through. This results in strong wear on the seals and piston rod guide, mostly ending in a loss of oil and, thus, performance of the shock absorber.
To prevent these distortions and defects, workshops should ensure to not tighten the shock absorbers firmly when the axle is suspended. Only tighten them when the vehicle stands on its wheels, or when the wheels are pressed upwards with tools such as hydraulic jacks.
If shocks are installed under tension or a fastening nut is tightened too firmly, the pin joint can tear out.
To prevent this, and overall material overexpansion due to excessive tightening torques, always ensure that impact wrenches are not used when performing this work and that the specified tightening torque is observed.

The risk of worn or defective shock absorbers
For vehicles with either worn or defective shock absorbers, or with an electronically adjustable chassis, safety can be severely compromised.
A vehicle’s stopping distances become longer if the contact with the road is no longer optimally ensured. Many electronic advanced driver assistance systems, such as ESP and ABS, require good contact of the wheels with the road to be able to function to their full potential.
The more electronic safety systems installed in the car, the more the performance of the shock absorbers comes into play.
Short stopping distances are only possible with functional shock absorbers, such as defective shocks will reduce the brake force due to insufficient traction.
Depending on speed, vehicle systems and road surfaces, the stopping distance can increase by up to 20 percent, which can be as far as six metres for speeds up to 80 kilometres an hour.
If the shock absorbers no longer prevent the car body from pitching and vibrating, then it becomes more difficult to control the vehicle during evasive manoeuvers, its cornering ability generally becomes unstable and the car is then prone to aquaplaning.
Furthermore, worn shock absorbers will adversely affect other components in the vehicle, with tyre and chassis parts, such tie rod ends and steering devices, exposed to greater wear.
An oil leak is a clear indication of a defective shock absorber; however, the shock absorber may be defective, even if no oil spills are visible. A professional inspection at a specialised workshop is therefore essential.

For more detailed information please visit www.zf.com/au