Checking Shock Absorbers

Springs are what support the car and allow the suspension to bounce smoothly over bumps and other road irregularities. The shock absorber's function is to moderate the spring action-to quickly slow the bounce and help the spring return to its normal position. Shock absorbers do not require maintenance. An adequate supply of fluid is placed in them during manufacturing to compensate for small leaks. Minor leakage is acceptable if the shock absorber still functions correctly. Shock absorbers cannot be serviced, and need to be replaced when they lose their ability to control the suspension.

To the careful observer, a decline in shock absorber performance can be detected in normal driving. Worn shock absorbers will cause extra skittishness over bumps, and a less-controlled and wallowing feel in corners and after bumps. When seriously worn, the shock absorbers present little resistance to spring oscillations. Because they easily reach the limits of their travel, they may knock when going over bumps.

For more deliberate evaluation, the most common-though not entirely accurate-test of shock absorber function involves vigorously bouncing each end or corner of the car, and then releasing and observing how quickly the bouncing stops. More than one bounce usually indicates shock absorbers that need replacing.