On January 10, 2002, at 1345 hours Pacific standard time, an experimental Farrand Vans RV6, N164DF, ground looped on the landing rollout on runway 31L at the Reid-Hillview of Santa Clara County Airport, San Jose, California. The airplane was operated by the pilot/owner under the provisions of 14 CFR Part 91, and sustained substantial damage. The commercial pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed for the local area flight and no flight plan had been filed. The Safety Board Investigator-in-Charge (IIC) interviewed the pilot. The pilot stated that he had been practicing full stop landings. The sixth landing was the accident landing. He stated that there were no problems encountered during the landing. However, on the landing rollout, he came up on the brakes and the "tailwheel came around on him." The airplane ground looped and the left main landing gear collapsed. The pilot further indicated that he observed that the bolt from the left landing gear attachment was not in place and had most likely fallen out at some point, which lead to the left main landing collapsing during the turn to exit the runway. In the pilot's written statement to the Safety Board, he stated that on rollout, with the tailwheel on the ground, he applied the brakes to slow down. He stated that he was almost at a full stop before turning off the runway and "lost control because the left gear failed . . . . " The left landing gear collapsed and the airplane pivoted around the left wheel and slid into the dirt. A Federal Aviation Administration (FAA) inspector examined the airplane on-scene. There were no discrepancies observed with the left main landing gear, landing gear attachment assembly, or the associated bolt. He did note that there were skid marks at intersection Delta where the airplane attempted to exit the runway. The FAA inspector also interviewed the pilot. The pilot stated that he probably departed the runway at a high speed, and that the landing gear was not designed to take that great of a side load given the conditions and the relatively weak design of the landing gear attachment. ADDITIONAL INFORMATION On the day of the accident the airport manager had the runway inspected for foreign debris on the runway and did not find a bolt. The FAA conducted a subsequent search, and they also did not find the landing gear attachment bolt. Photographs taken by the airport manager of the accident airplane where it came to rest clearly show that the landing gear attachment bolt was in place.