Tour de France — the world’s most famous cycling race — began in 1903 as an effort to boost circulation for a sports newspaper. The race became an instant success despite its grueling nature. The Tour has evolved over the decades into a set of stages shorter than the early ones, but more numerous, so the race is of greater overall length. Some things are still familiar, for better or worse: how coveted the yellow jersey is, and how tempted some riders are to cut corners in the rulebook. This year’s riders set off Saturday — see today’s preview, with Saturday TV times, on Sports, Page C1.