Relationship of Vibration Frequency to Order of Vibration
After carrying out the road test as described in this article, the vibration was determined to be either vehicle-speed related or engine-speed related. That determination will identify the vibration frequency calculations that should be done.
| Vibration Type | Calculate |
|---|---|
| Vehicle-speed related | Tire-speed vibration frequency Driveshaft-speed vibration frequency |
| Engine-speed related | Engine vibration frequency Engine accessory vibration frequency Engine firing vibration frequency |
In calculating and using frequency readings, it is important to remember the direct relationship between Hz and rpm. One Hz is equal to 60 rpm. This is easy to remember by thinking of Hz as cycles per second. There are 60 seconds in a minute, therefore, multiply the Hz reading by 60 to get rpm. Conversely, divide rpm by 60 to get Hz.
Use the Frequency and RPM Calculations Worksheet to calculate system/component frequencies. The worksheet provides the necessary steps to determine each system/component group frequency.