On May 7, 1997, at 1900 eastern daylight time, a Piper PA-18-150, N4056Z, operated by a commercial pilot ground looped during a landing roll at the Presque Isle County Airport, Rogers City, Michigan. The 14 CFR Part 91 flight was operating in visual meteorological conditions without a flight plan. The pilot and passenger were not injured. The airplane was substantially damaged. The flight originated from Alpena, Michigan, at 1700 edt. The pilot reported that during the landing roll on runway 09 (3,017' x 60', asphalt) the tailwheel began to shimmy. He reported that the spring on the left side of the tailwheel became disconnected which resulted in a loss of steering control. He reported the groundspeed was too slow to have any rudder authority. The airplane ground looped 270 degrees to the right during which time the left wing struck the ground. The airplane traveled off the right side of the runway into the grass prior to coming to rest.