Tire and wheel vibrations are the second level of testing
for low-frequency vibrations that are vehicle speed sensitive. The tires,
wheels, brake rotors and brake drums are usually to blame, and are systematically
tested.
First-Order Tire and Wheel Vibration
| • | First-order tire and wheel vibrations are vehicle-speed-related.
The vibration is not related to the tires or wheels if the engine speed affects
the vibration, or if the vibration is eliminated when the transmission is
placed in Neutral. |
| • | Vibrations that are felt in the steering wheel are usually related
to the front tires or wheels. Vibrations that are felt in the seat or in the
floor are usually related to the rear tires or wheels. |
| • | The customer may complain of a WADDLE at low speeds of 8-56 km/h
(5-35 mph). |
| • | The EVA frequency corresponds to the first-order of tire rotation,
usually in the 10-20 Hz range. The range depends on the complaint
speed and the tire size -- smaller tires rotate faster at any given speed. |
| • | First-order vibrations rarely exhibit noise. The frequency range
of the human ear begins at 20 Hz. An exception to this would be if
the tires are worn irregularly, producing a GROWLING or SLAPPING noise. |
