The number of impulses per revolution of the wheel is the ratio between the moment of occurrence of natural oscillations of the corresponding suspension, expressed in terms of the speed of movement, and the speed of movement at the moment of occurrence of vibrations. There are two types of imbalance.
Unbalance: mass unbalance = 1 impulse per wheel revolution.
Radial runout: geometric deformation = one or more pulses per revolution of the wheel. Vibrations occur on the following nodes and parts:
- rotating elements (tires, wheel rims, decorative wheel caps, brake mechanisms, wheel drive shafts, hollow side gear of the open differential type manual gearbox);
- damping elements (shock absorbers, mountings and/or damping elements for suspension, subframe, rack and pinion steering, steering column, seats, etc.).