The Tour of Flanders is Belgium's most brutal day in the saddle. The bike-crazed Flemish don't just send riders over cobblestone roads. Nor are they content to break the racers' legs with nearly 20 steep hills. No, the worst of all cycling worlds meet in Flanders with narrow, vertical roads paved with slippery, dangerous cobbles. The hills are so steep they are called "muurs", or walls, and they come one after another, for hours, until the riders...