Alberto Contador of Spain won this year's Tour de France by only 39 seconds, one of the narrowest margins of all time. And while it's impossible to say for sure that none of the riders doped, there wasn't a single positive drug test.

What's significant about these two developments—the razor-thin victory margin and a possible decline in chemical enhancement—is the effect they seem to be having on cyclists and their teams. This group, which is plenty obsessive to begin with, has become increasingly consumed with the search for...