The Loire à Vélo is probably the gentlest introduction to multi-day cycle-touring that France offers, and it earns that reputation honestly. For most of the 900 kilometres between Tours and Saint-Nazaire you are rolling along a broad, mostly flat valley floor, the river always close by, the horizon broken by the silhouettes of Chambord, Amboise, or Villandry depending on which stretch you have reached.
Elevation gain is negligible on the valley floor itself, though a handful of short, stubby climbs appear where the route briefly leaves the levee and cuts through vineyard country above Saumur or Muscadet.
The surface is generally excellent. A large proportion of the route runs on dedicated tarmac paths separated from traffic, particularly between Blois and Angers, so you can genuinely relax and look around. Narrower stretches through villages and wine estates do share quiet country roads, but traffic is light and motorists here are accustomed to cyclists.
Riding west, from Tours toward Saint-Nazaire, keeps the prevailing Atlantic wind at your back most of the time, which matters over 900 kilometres. Most riders split the distance into seven to ten days, staying in the absurdly convenient network of gîtes and riverside campsites that have sprung up along the route.
Bike hire is available in Tours, Blois, Angers, and Nantes, and the SNCF TER trains connecting these towns accept unboxed bikes, so point-to-point logistics are straightforward.
The châteaux do become a little repetitive after the third or fourth, but the picnic lunches of local goat's cheese, Vouvray, and baguette on the riverbank are not. Culture and calories balance each other well here.
Late April through early June or September gives you cool temperatures, dry roads, and far fewer rental cyclists clogging the path at Chambord.