What is shimmy?
Shimmy means that when you driving a car in certain speed, no matter the self-excited vibration generated by the internal cause or the forced vibration caused by external factors, can lead to front wheels drastic swing side to side, as a result, “hand jouncing”(also called shivering)at steering wheels will occur, drivers can’t control steering wheels when it is severe, this is one of the common severe failures while you driving a car. Shimmy always starts when you driving vehicles in a certain speed, it often appears in medium and high speed driving, seldom in a low speed. Shimmy will reduce the comfort performance provided for passengers, increase fatigue degrees of drivers, consequently, it makes serious negative influence on driving security of a car and work life of car parts.

The Cause of Shimmy
　　There are many causes that can result in the shimmy of front wheels. These causes are often complicated. Vehicle structures, road situations, the way of driving, maintenance, adjustment and other factors can generate above-mentioned bad results.
The front wheels are connected to the structure of a vehicle through a suspension system and a steering drive gear, these machines linked together compose a complex vibrating system, this system has its own natural frequency, when internal or external bumping frequency is close to its, acute oscillation will happen, which can result in excessive vibrations of vehicles, amplitude and frequency will be getting larger and larger and can not stop by itself, this is shimmy.

How to eliminate shimmy
　　The natural frequency of the system is determined by a vehicle system’s damp. A vehicle system’s damp can be improved by adjusting each system of the chassis, but due to the complex structure of the chassis, and various parts, it’s hard and takes time to find out root causes of the problem. Usually, we are just getting half the result with twice the effort. The application of steering damper can immediately improve system damp of a vehicle, eliminating shimmy of a vehicle, as well as increasing comfortable ride and the driving stability of a vehicle.

The Familiar Causes of Shimmy
- Deficiency of system damp (essence cause).
- The toe-in is too large.
- Front hub bearing is not fastened in place (or damaged).
- The displacement tolerance of a steering wheel is too large.
- Front axle is deformed; cross torsion bar ball joint pin and its ball joint knuckle are loosened and/or worn; fastening screw is loosened and/or dropped out; king pin of steering knuckle (vertical shaft) and its bush are worn.
- The front steel springs is un-level, spring elasticity is uneven in the right and left. The U- bolt is loose, the front steel spring pin is worn, shock absorbers are failed, etc..
- The imbalance of wheel assembly, and added tyre cushion at the inner side of front tyres or additional welding to the circular rim (steel ring) can force wheels to generate centrifugal force.
- Steering gear driving device is excessively worn, and the steering fixed bolt is loosen.
- Steering damper are damaged or failed.