How the Superman - Flash Races First Started
According to issue #199, the Secretary-General of the United Nations came up with the idea, and approached Superman and the Flash with the idea of a benefit race. Money raised from sweepstakes would fund aid programs for underdeveloped nations. Superman and Flash completed the race with a clear tie, ensuring that everyone was a winner.
Superman went on to race Barry Allen several more times, and also held races with Wally West and even Jay Garrick. All three of those men who wore the Flash costume at one point or another would beat Superman at least once in a footrace. Superman, who was able to force a couple of ties, has never outright won a race with a Flash.