On January 23, 2008, at 1015 central standard time, a Beech 58, N4626A, operated by Flight Express, experienced a right main gear collapse upon landing at the St. Louis/Downtown Airport (CPS), Cahokia, Illinois. The commercial rated pilot was not injured. The airplane was substantially damaged. The 14 Code of Federal Regulation Part 91 was operating in visual meteorological conditions without a flight plan. The local flight originated from CPS at 0920. An annual inspection had just been completed on the airplane and the pilot was performing a maintenance test flight. The pilot reported that after departure he climbed to altitude to check the flight controls and aircraft performance. He reported he cycled the landing gear several times, each time receiving a down and locked indication. The pilot then flew to the Scott Air Force base/Mid-America (BLV) airport to practice an approach and landing. The pilot stated that during the landing roll he felt "a falling motion to the back right" at which time he applied full power and took off. The pilot contacted the air traffic control tower and asked them to visually check the landing gear. The controller reported the gear appeared to be down. The pilot then returned to CPS to land. He reported having a gear down and locked indication, but stated that during the landing roll, the right wing seemed closer to the ground than normal. Again, he aborted the landing. He requested that the CPS air traffic control tower visually check the landing gear. The controller replied that it appeared down, but that it looked "weak" during the landing roll. The pilot then climbed to altitude to troubleshoot the landing gear. He reported he used the Emergency Gear Extension checklist and during the manual extension process, he was only able to turn the extension handle 1-1/2 turns. He made another fly-by the tower for a gear check and was informed that it appeared to be down. The pilot then used the Gear-Up Landing emergency checklist and landed the airplane. During the landing roll the right main gear collapsed and the right wing contacted the runway. As a result, the right wing and aileron were substantially damaged. The investigation revealed that the leg brace portion of the landing gear retract brace assembly was replaced during the annual inspection. The leg brace that was installed was not purchased from Beechcraft. According to Beechcraft they do not sell the leg brace as a separate item from the upper brace assembly because of the close tolerance required between the two braces in order for the gear to properly lock in the extended position. In reference to the nose gear, the BE-58 maintenance manual states that the upper brace assembly and the leg brace must be replaced as a unit. It does not state this information in reference to the main landing gear. A Federal Aviation Administration Inspector from the St. Louis, Missouri, Flight Standards District Office reported that after the accident, with the right gear extended, he was able to release it from the locked position by pushing on it with his hands.