ASE A4 Suspension and SteeringWheels and Tires Diagnosis and RepairHard
A technician is inspecting a vehicle with a severe vibration complaint. During the inspection, they notice that one of the wheel weights has fallen off. After re-balancing the wheel, the vibration is significantly reduced but not entirely eliminated. The vehicle still exhibits a slight vibration at highway speeds. What should the technician consider next to fully resolve the vibration?
- ACheck for excessive positive camber.
- BPerform a road force variation (RFV) measurement.
- CReplace the shock absorbers and struts.
- DInspect the brake rotors for runout.
Show answer & explanationAnswer & explanation
Correct answer: B. Perform a road force variation (RFV) measurement.
If a wheel is balanced but a vibration persists, especially at highway speeds, it often indicates a non-uniformity issue within the tire or wheel assembly itself, such as high or low spots, which is measured and corrected by a road force variation machine.
Why the other options are wrong
- A. Camber issues primarily cause tire wear and pulls, not vibrations after balancing.
- C. Worn shocks/struts would likely cause cupping wear, poor ride, or bouncing, but a persistent vibration after balancing points to the tire/wheel assembly itself.
- D. Brake rotor runout causes a pulsation felt in the brake pedal when braking, not a continuous vibration at highway speeds.
Road Force Variation (RFV)
Road Force Variation (RFV) measures the uniformity of a tire and wheel assembly under load, identifying high/low spots that cause vibrations not correctable by traditional balancing.
- Measures tire/wheel uniformity under load
- Identifies non-balance related vibrations
- Can optimize tire-to-wheel mounting position
Memory trick: Balanced but still shaking? Road force is the missing link!