We are taking the Corail from Paris to Amboise. We stay at Le Manoir de la Maison Blanche B&B. We plan to use the bike to visit the chateaux and enjoy the country side. We will be at Amboise at mid May. Is it possible or do we need to rent a car? Thank you.

you do not need to rent a car. The plateau to the south of the B&B is only about 100m metres up, all else is riverside. Roads are generally safe for bikes

Many roads are rural - narrow and winding (Chateaux are typically located in small villages or the counryside - not towns or sidwalks)and traffic will be moving fast. If you're comfortable biking under these condtions over fairly long distance it could work. Which chateaux do you want to see. Have you mapped out the distances?

(We could comfortable see 2 per day with a car - with a bike you would be limited to one.)

but you just put the bike on a train if you want to go further

This is my first time to stay in the Loire Valley. Last time I came on a tour from Paris. I just love the tranquility of the country side. That is why we decide to stay over. The chateaux I like to see are Chenonceaux, Chambord and d'Amboise. I will do some serious mapping this week-end. I did not know that the train can take you further.
Bilboburgler-- any more tip for me to get the bike. How do we get to Le Manoir de la Maison Blanche from the train station? We are fit enough to drag our luggage and walk. Thank you so much for all the inputs.

The ride from Amboise to Chambord is a bit much unless you are an experienced cyclist (60-70 miles round trip). And I don't know if I'd do it with a bike that my rear end was not used to!

The trip to Chenonceaux is very doable. I haven't done it from Amboise but have done it twice from Onzain - Excellent! The ride from Amboise to Chaumont would be nice.

If possible, stick to roads that are white on a Michelin 1:2000,000 map. Virtually no traffic and the French drivers are much more courteous to cyclists than American or British drivers.

'fraid its google maps as usual. the station will be called "Le Gare" as I guess you know