Meetya

Check out this awesome training document (see attachment) I just found on all kind of Noise, Vibration, and Harshness for our Lexuses.
Here is what it covers:

• Prevention of Vibration and Noise
• Preventing Vibrating Force from Occurring
• Isolating Vibrations
• Body Shake
• Steering Flutter
• Steering Shimmy
• Steering Shimmy
• Shift Lever Vibration
• Body Booming Noise
• Vibration During Braking
• Brake Squeak
• Types of Wind Noise
• Identifying Wind Noise
• Diagnostic Procedure for Wind Noise Concerns
• Squeaks, Rattles, & Interior Noise

My favorite parts:

Steering Flutter
Steering flutter is a condition in which the steering wheel oscillates 5 to 15 Steering Flutter times per second in the direction of the turn. It occurs at relatively limited but high speeds between 80 and 120 km/h (50 and 75 mph), and the oscillations on the steering wheel are fairly constant.

Main Causes:

• Tire run−out, unevenness, or imbalance
• Resonance between the tires and the steering wheel

Mechanics of Noise Development:

1. Any run−out or imbalance in a tire will generate a vibrating force while the vehicle is in motion.
2. This vibrating force generates an inertial moment at the kingpin, causing the tires to vibrate laterally. The steering wheel will oscillate laterally as well.
3. At a certain speed, the lateral vibrations of the tires generated by the centrifugal force resonate with the steering system, causing the steering wheel to oscillate clockwise and counterclockwise.

Steering Shimmy
This is a condition in which the steering wheel oscillates clockwise and counterclockwise, just as in steering flutter, but at lower vehicle speeds (e.g., 60 to 80 km/h [38 to 50 mph]). This symptom traces its origin to uneven road surfaces or to braking when tires or brakes are unevenly worn. The oscillation of the steering wheel increases with the vehicle speed.

Main Causes

• Uneven road surface.
• Tire deformation or an abrupt vertical vibration caused by braking when tires or brakes are unevenly worn.
• Resonance 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.

An uneven road surface, and deformations in the tires or vertical oscillations upon braking all can trigger vibrations around the front kingpin, causing the steering wheel to shimmy. The components that transmit these vibrations and their symptoms are identical to those of steering wheel.

NOTE: Although steering flutter and shimmy are identical, they have different origins. Flutter is forced upon the steering wheel system resonating with tire vibrations, which are caused by imbalance, run-out, or unevenness in the tires. Steering shimmy, on the other hand, is a self-perpetuating oscillation triggered by braking or an uneven road surface.

V300Graham

Fantastic and very informative.

I'm going to check my axles for run-out damage now, thanks !!