Note. In the presence of a defect in the design of the tire, balancing weights of a very large mass are usually installed on the wheel (50 g or more on one side of the wheel rim).
«hardening» suspension shock absorbers
There are cases of «vibrations» only on particularly smooth roads (on freeways or new express lanes). Friction in the shock absorbers, combined with a stiff suspension, can cause vibration-like bounce. This phenomenon stops under normal driving conditions (during a normal overtaking maneuver, on a rougher road surface, etc.) Check the tightening torques of the threaded connections and the condition of the hangers. After installing new parts or on a new vehicle, this phenomenon gradually disappears as «lapping» details.
Excessive tire pressure
When tires are overinflated, a rebound phenomenon occurs, which can be mistaken for vibrations.
Troubleshooting
Check 1: road test to determine the nature of vibrations and their sources
Mark the position of the tire on the wheel rim (for less visibility, apply a mark on the metal on the inside of the wheel).
Play vibrations, make sure they are related to the speed of movement (reproduce vibrations in several gearbox gears)
Record the speed range in which the vibrations occur.
Vibrations of the front or rear suspension at one impulse per wheel revolution
Check the effect of braking on vibrations:
- Slow down the car slightly in the area of vibrations (until the brake pads touch the disc) and determine the presence or absence of a change in vibrations, under-
- maintaining the speed. Check the effect of changing engine torque (movement «tightness» lower gears):
- change the motor load in the area of vibration occurrence rates (to create traffic conditions «tightness», then when switching to lower gears) and determine the effect of this change on the vibrations.
Determine from which of the suspensions the vibration comes, and the number of impulses per revolution of the wheel according to the table of the rates of occurrence of natural vibrations of the suspensions.
Check 2: road test to determine the rate of occurrence of natural oscillations of the suspensions
This test is to determine the rate of occurrence of natural oscillations of the suspensions by artificially creating an imbalance (receiving one impulse per wheel revolution) on one of the front, then on one of the rear wheels.
The best solution is to use another vehicle for this test (the same model, but not necessarily the same engine. Install an additional 50 g balance weight on one of the front wheels and mark its position (the position of the weight on the circumference of the wheel disk does not matter). Leave the old weights or the weight in place.
Carry out a road test and record the speed range in which the vibrations appear. The result corresponds to the rate of occurrence of natural oscillations of the front suspension of the tested vehicle.
Remove the extra weight from the front wheel.
Install an additional weight on one of the rear wheels.
Carry out the road test again and note down the speed interval in which the vibrations appear, the result corresponds to the rate of occurrence of natural oscillations of the rear suspension of the tested vehicle.
Compare the result of test 1 with test 2 and determine which of the suspensions is the source of the vibrations and the number of pulses per revolution of the wheel.
Check 3: road test to check for defects in tire construction
A possible cause of vibrations is a defect in the internal structure of the tires. Such a defect is outwardly invisible. To identify it, rearrange the front and rear wheels (put left wheels on the left, right wheels on the right), having previously recorded the interval of vibration speeds when performing test 1 and perform test 1 again.
If, during this new test, the interval of vibration occurrence rates has changed and began to correspond to the rate of occurrence of natural vibrations of another suspension (see table «The rate of occurrence of natural oscillations of the suspensions»), the defect is related to tires or wheel balancing.
Note. In the presence of a defect in the design of the tire, balancing weights of a very large mass are usually installed on the wheel (50 g or more on one side of the wheel rim).
The reliability of test 3 results is based on the difference between the natural oscillation speeds of the front and rear suspensions.