Diagnostic inspection and testing suspension

Suspension problems can usually be isolated and at least partially diagnosed by careful observation of the symptoms and inspection of the components that are the most likely cause.

Torsion bars support the weight of the car and allow the suspension to travel smoothly over bumps and other road irregularities. A torsion bar that is twisted (loaded) by a bump simply unloads in the other direction with nearly the same force that loaded it.

The function of a shock absorber, or damper, is to moderate the torsion bar action. It slows the bounce and helps the torsion bar return to its normal position. Shock absorbers require no routine maintenance and cannot be serviced.

The best evidence of failing shock absorbers is their behavior in normal driving. Worn shock absorbers will allow extra skittishness over bumps, and a less-controlled and wallowing feel after bumps and in corners. When seriously worn, the shock absorbers present little resistance to torsion bar oscillations. Because they so easily reach the limits of their travel, they may knock when going over bumps.

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 suggests that the shock absorbers are not properly damping the torsion bar action and need to be replaced.

Differences from side to side will affect handling and stability. It is strongly recommended that shock absorber cartridges or strut bearings be replaced in pairs.

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