Tire and wheel assembly vibrations are the next level of
testing for low-frequency vibrations that are vehicle speed sensitive. The
tires, wheels, brake rotors and wheel hubs should be systematically tested,
according to the symptoms.
First-Order Tire and Wheel Assembly Vibration
The following are symptoms of first-order vibrations caused by tire
and wheel assemblies:
| • | The vibration is always vehicle-speed related. |
| | If the vibration is affected by the speed of the engine, or is eliminated
by placing the transmission in NEUTRAL, then the vibration is not related
to the tire and wheel assemblies. |
| • | The vibration will feel like a SHAKE, usually in the steering
wheel or the seat: |
| - | Tire and wheel vibrations that are felt in the steering wheel
are most likely related to the front tire and wheel assemblies. |
| - | Tire and wheel vibrations that are felt in the seat or the floor
are most likely related to the rear tire and wheel assemblies. |
| - | This may not always hold true, but is a general rule that may serve
to initially isolate a problem to the front or the rear of the
vehicle. |
| • | The customer may complain of a WADDLE at low speeds of 8 to 56 km/h
(5 to 35 mph). |
| • | The frequency on the EVA will correspond to the first-order of
tire rotation. This frequency will usually be in the 10 to 20 Hz
range, depending on the speed of the complaint and the size of the tire. The
smaller the tire, the faster it will rotate at any given speed. |
| • | The range of the human ear begins at 20 Hz. For this reason,
first-order tire vibrations are rarely produce noise. The exception to this
would be if the tires display an irregular tread pattern or flat spots, causing
a GROWLING or SLAPPING noise. |
