What was found
DURING INITIAL TAXI NOTICED AN UNUSUAL VIBRATION AND BOUNCING EFFECT SIMILAR TO A FLAT TIRE CONDITION. I ADJUSTED THE TAXI SPEEDS AND MADE SMALL TURNS AND THE PROBLEM WOULD COME AND GO. WHEN APPROACHING THE DEPARTURE END OF THE RUNWAY CONDITION IMPROVED. DURING TAKEOFF ROLL A MODERATE VIBRATION RESUMED SUDDENLY AT APPROXIMATELY 65K. DECISION TO REJECT THE TAKEOFF CAM AT APPROXIMATELY 70-75K, LIGHT BRAKING. ABORTED TAKE OFF. REMOVED FROM SERVICE. C/W AMM TASK 05-50-24-200-801-A, NO DEFECTS NOTED. TAXIED A/C NO VIBRATIONS NOTED, NO PARTS REPLACED. AIRCRAFT RETURNED TO SERVICE.