The pilot reported that the airplane touched down on the left and right main landing gear wheels. A few seconds later, the pilot felt that something failed on the left main landing gear, and the left wing began to drop to the runway. The left wing contacted the runway, and the pilot attempted to maintain directional control. Subsequently, the airplane exited the runway surface, which resulted in substantial damage to the left wing, left aileron, and horizontal stabilizer. Maintenance records revealed the main landing gear were overhauled about two months prior to the accident. The pilot reported he had completed about 8 to 10 takeoffs and landings during those two months. Postaccident examination revealed the main landing gear system was improperly rigged and the improper installation of hardware which resulted in the overstress failure of the left main landing gear system.