The pilot reported that following his uneventful landing in variable and gusty wind conditions and as he was about to make a 120-degree left turn to exit the runway onto the taxiway, the airplane would not straighten despite rudder and brake inputs. The airplane continued the left turn and exited the taxiway into the grass and struck a taxiway sign. The airplane sustained substantial damage to the forward fuselage. A Federal Aviation Administration inspector conducted a postaccident examination of the airplane’s brake system and reported that there were no mechanical failures or malfunctions that would have precluded normal operations. At the time of the accident, the pilot was making the turn off runway 35R with wind from 040o at 7 knots. However, during the previous hour the wind was variable from 140o to 240o creating the potential for windshear.