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Aircraft Tire Balance & Vibration

1. Tire inflation pressure particularly under inflation

Note: if your aircraft maintenance manual lists a 4 ply tire then the inflation pressure is for a 4 ply tire and not a 6 ply tire. For example, the 6.00-6 4 ply Air Hawk tire has a generic* inflation pressure of 29 psi. while the 6 ply Air Hawk has a generic inflation pressure of 42 psi. If you put a 6 ply tire on the airplane that was spec'd for 4 ply and lists 4 ply pressure of 29 psi then you are under-inflating the 6 ply tire. This may lead to tire damage and vibration problems.

* I say "generic" because these are the tire inflation pressures from the tire manufacturer, Specialty Tire per their letter dated September 18, 2002. The inflation pressure that the airframe manufacturer recommends may be different because of airframe requirements such as landing gear stress, etc.

2. Incorrect tire or tire weight. Check your aircraft maintenance manual for the correct tire and correct inflation pressure.

3. Flat spot on tire.

4. Tire too stiff

5. Worn landing gear components particularly on Cessna aircraft.

6. Tire and wheel imbalance. Cessna uses a tight 5 inch oz. as maximum imbalance.

The valve stem should be aligned with the red dot or triangle ( indicates the circumferential location of the light spot on the tire). Goodyear tubes are marked with a yellow stripe indicates the heavy spot, if no yellow spot then the valve is considered the heavy spot.

Tire Cross Sections

Compare these photographs of cross-sections of 6.00-6 6 ply tires.

From top to bottom:
Goodyear Flight Custom III
Michelin Air
Specialty Tire Air Hawk
Notice that the Goodyear tire has much more tread rubber than the other tires. Tread thickness of the Air Hawk and the Michelin are comparable.

Cross section comparison of Goodyear Flight Custom III (thicker tread) and Specialty Tire Air Hawk

Cross section comparison of Goodyear Flight Custom III (thicker tread) and Michelin tire