Travis Brown raced a prototype belt drive cyclocross bike at the Vegas Cross race at Interbike on Wednesday night. The bike has unique tension adjusters built into the dropouts. Travis was equipped with a few "cog" options so he could make a final gearing selection at the race once he saw the course. The bike was built off a standard XO2 platform and had the rear dropouts and chainstays replaced to accommodate the belt. The chainstays are off a Trek T900 tandem; their heavier gauge minimizes lateral flex and compression loads that could make the belt skip.
Trek's Advanced Concept Group has been tinkering with how belt drive bikes can fit into the line. Right now belts are on a few commuter models (including the District) and some other prototypes running around the office but watch for them on more and more bikes in the future.