It can, however, be assumed that in most cases of transmission of vibrations to the steering wheel, they come from the front suspension and are transmitted through the steering. But this is also not an absolutely universal rule. Steering wheel vibrations can be caused by some very specific rear wheel tire defects.
Vibrations are caused by a sequence of pulses (blows), coming from elements rotating with the wheel. Vibrations are caused by two types of causes:
- imbalance - mass imbalance;
- one pulse per wheel revolution.
The front and rear suspensions have characteristics on the basis of which diagnostics are carried out. They dampen vibrations, except for those that have a frequency «natural vibrations».
The moment of occurrence of natural vibrations of the suspension depends on its longitudinal stiffness. The oscillation frequency is determined through the speed of the vehicle. The moments of occurrence of natural oscillations of the front and rear suspensions differ from each other.
Vibration diagnostics allows you to determine which suspension (front or back) they come out, and, in particular, to determine the number of impulses per revolution of the wheel. These initial diagnostic data serve as a guide to the selection of the necessary technical intervention. Therefore, it is important to obtain this data from the owner or to carry out a road test.
The amount of unbalance needed to create perceptible vibrations is about:
- 20g for wheels (tires on 15" rim);
- 100 g for brake disc or drum;
- 500 g for the wheel hub;
- 1.16 kg for the wheel drive shaft.
Some types of vibrations caused by the operation of the engine can be mistaken for vibrations associated with the speed of movement. In this case, the appearance of vibration is most likely associated with engine speed or load. This can only be verified by reproducing the fault with an appropriate check.