The airplane bounced once during landing on the dry, paved runway. The pilot stated that as the airplane settled, the left wheel began to vibrate, and then the airplane ground looped to the left. Postaccident inspection revealed the inner tube inflation valve stem sheared off, and the wheel halves fractured. No preaccident mechanical anomalies were discovered during the inspection. The wheels had been installed 4.5 service hours, and 7 landings prior to the accident.