MONS-EN-PÉVÈLE, France—When Daniel Accou closes his eyes, he sees cobblestones. Half a century of working on them will do that to you. On winding roads all over the Nord-Pas de Calais region, here by the Belgian border, he laid and re-laid them until he was doing it in his dreams.

“The cobbles are my religion,” he said.

Bicycle racing is a...