Steering Shimmy Symptoms And Malfunction Causes


This is a condition in which the steering wheel oscillates clockwise and counterclockwise, just as in steering flutter, but at lower vehicle speeds; generally less than 80 km/h (50 mph). This symptom traces its origin to rough road or to braking when tires or brakes are unevenly worn.
1.Main causes
Bumpy road.
Tire deformation or an abrupt vertical vibration caused by braking when tires or brakes are unevenly worn.
Resonances among tires, the steering system, and the suspension.
Play in the steering linkages, a decrease in resistance due to wear, or lack of hardness or rigidity of the steering linkages.
2.Mechanics of vibration development
A bumpy road, deformations in the tires, or vertical oscillations upon braking can all trigger vibrations around the front kingpin, causing the steering wheel to shimmy. The components that transmit these vibrations, and the symptoms of the vibrations, are identical to those of steering flutter.
Although steering flutter and shimmy seem to be identical, they have different origins. Flutter is forced upon the steering wheel by the steering system resonating with tire vibrations which are caused by imbalance, runout or unevenness in the tires. Steering shimmy, on the other hand, is a self-perpetuating oscillation triggered by braking on a bumpy road.

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