We have actually done two bicycle trips in the Loire Valley, in addition to one car trip. The bike trips were more fun, and we saw so much more (you take time to smell the roses, so to speak.) For those of you (like me!) who aren't really bikers, rest assured: you too can do this! I was never on a bicycle with gears until I was 40, and had such a death grip on the handlebars that I was exhausted in a mile--but with a little practice, reached the point where I can happily bike 40 miles a day with no special effort.
We have biked the Loire in two very different ways: our first time, my husband and I and two friends did an unsupported trip (i.e., carried our worldly possessions on our bikes), stayed in inns, and designed our own itinerary. The second time, with our (13 & 15-year-old) sons, we took a Backroads biking/camping trip. This was a supported trip, meaning that the Backroads van took our belongings from campsite to campsite, and provided a 'sag wagon' for those who chose to get a lift rather than bike every inch of the route. I definitely recommend the supported approach with kids--though mine were almost old enough (and strong enough bikers) to go unsupported on this trip. In fact, my younger son celebrated his 13th birthday on the trip by doing his first 'metric century'--65 miles (100 km) in a day.
The unsupported trip was, in some ways, more fun. We got off the beaten path, and stayed in inns (read: warm and dry, at least at night). I am getting a bit old to look forward to sleeping on the ground... On this trip, we also went north of the heavily travelled Loire Valley and bike along the valley of Le Loir. It was here we saw the fabulous troglodyte caves, and here we found our two favorite accommodations. The biking was best here, with so little traffic, though there weren't the chateaux to visit around every corner.
For the details of these trips, see the other entries in this journal--accommodations and sights.