Testing your shock absorber

20 Nov, 2014

A large number of factors influence shock absorber performance and service life. Road conditions, load levels, mileage, driving style, and environmental influences such as cold, heat, dust, dirt, and salt water cause considerable wear and tear.

The risks of defective shock absorbers:

Shock absorbers are only rarely subject to sudden breakdowns. Instead, they wear down slowly, which means that drivers gradually become accustomed to lower levels of damping performance.

Shock absorbers with lower performance levels can have dangerous consequences, especially in critical driving situations:

■ The vehicle is harder to handle in curves, and may fishtail.

■ The vehicle is strongly affected by lateral winds.

■ Longer braking distances.

■ The shock absorbers bottom out if the vehicle drives over large bumps or potholes.

■ There is a higher risk of hydroplaning, and the driver can lose control of the vehicle.

 We recommend regular testing for the suspension.

Adequate Testing Methods:

■ A suspension / shock tester is a practical system and highly recommended for workshops. It detects deficiencies in only a few minutes, and presents the results as a graph. When the graph is compared with safety values, it yields a clear indication of the suspension's operational reliability and safety.

■ A comparative road test with a new vehicle of the same type can also provide an indication of suspension performance.

■ A visual inspection of the suspension is an essential part of testing at professional workshops. It enables some types of damage to be identified right away:

• Distinct traces of oil on the shock absorber: Be careful!

This should not be confused with the residue that remains from the normal level of oil mist around the upper part of the shock absorber, or with road dirt or underbody sealant that collects on the container tube.

• Worn compression stops.
• Unusual wear patterns on the tires.

Inadequate testing methods:

■ Rocking method: The car body is pressed down above the wheel and immediately released. The time it takes for the body to stop oscillating up and down is supposed to indicate how well

the shock absorber functions. However, since this test does not simulate the rebound and compression forces in the range relevant for safety, it can only provide a subjective assessment.

■ Manual testing: The shock absorber is extended and compressed by hand. This method can only identify complete failure.

When to replace?

Shock absorbers lose their damping ability over time and as a rule Sachs recommend inspection every 10,000Klms. Replacement at 80,000klms will ensure optimum ride quality.

Related suspension components should also be replaced at 80,000klm with emphasis on strut mounts, bearings, bump stops and shock dust covers as these components are also critical to vehicle handling and shock absorber performance. For example a split or cracked dust cover makes a vehicle by law not roadworthy.