Mangeas is from Saint-Martin-de-Landelles in Normandy, he was born in Mortain (Manche). He comes from a cycling family. He saw the for the first time at the age of four.
He also watched his cousin ride.
He worked as a baker for 10 years in Saint-Hilaire-du-Harcouët before being discovered by Albert Bouvet, the deputy director of the Mangeas recounted in an interview with Vélo 101 that he had commentated on table-football games among friends when he was a child, and commented on his first bike race when he was 15 years old.