Vibration, shimmy and other similar conditions are usually blamed on improper tire balance. Imbalance is a well-known and easily understood cause for vibration. In many cases though, this may not be the cause. There are a number of specific aspects of the tire, wheel and gear assembly which can be the cause or contribute to aircraft vibration. As with any concern, a systematic approach should be taken to isolating its cause.

  • Check that the tire has been inflated to the proper inflation pressure.
    • Follow the airframer's recommendation.
    • Be sure an accurate calibrated pressure gauge has been used.
  • Check that dual tire inflation is equalized between tires and per the operating specification.
  • Assure that the tire reached full growth before it was installed on the aircraft.
    • Allow at least 12 hours at operating or rated pressure for the tire to attain full growth.
  • Check that the beads of the tire have been properly seated.
  • Check the tire for flat spotting or uneven wear. If flat spotting does not extend to the protector ply (Radial) or reinforcing ply (Bias) and vibration is acceptable, the tire can be left in service.
  • Verify that tires have been properly mounted. For tubeless tires, the red balance mark on the lower sidewall of the tire should be aligned with the wheel valve. For tube‑type tires, the balance mark (light spot) on the lower sidewall of the tire should be aligned with the balance mark (heavy spot) on the tube.
  • Check for air trapped between the tire and tube. Use a soapy solution to check for leakage at the base of the tube valve stem where it exits the wheel. Rolling the tire by taxiing will generally work any trapped air out from between the tube and tire.
  • Is the tube wrinkled because of improper inflation procedures?
  • Is the wheel out of balance because of improper assembly?
    • Follow the wheel manufacturer's instructions for properly aligning wheel halves.
    • The balance mark on the tire should be aligned with the valve mounted on the wheel, unless otherwise specified by the wheel manufacturer.
  • Check the condition of the wheel to see if it has been bent.
  • Check for a loose wheel bearing caused by an improperly torqued axle nut
  • Check for poor gear alignment as evidenced by uneven wear
  • Check for worn or loose landing gear components.

Certain aircraft have nose landing gears which are sensitive to vibration. For these cases, assemblies should be checked for balance and wheel weights added when required