We will be in France from Sept 1 to 21. We are thinking of riding NE from CTG toward Reims. We're thinking Champagne, Burgandy then West to Loire Valley before spending our last 5 days in and around Paris. We can easily cover 50 to 75 miles a day. Your thoughts and tips are appreciated.
I think it is a marvelous idea and you have picked a great time of year for it.
It's a great way to see the country and the land, experiencing it in your lungs and muscles as well as your eyes and stomachs.
My experience cycling in Europe is limited to some day trips and a week touring Burgundy. For me the most difficult part was itinerary planning. I found the IGN topo maps to be very useful and the Lonely Planet book about biking in France to be suggestive, at least where its itineraries meshed with mine. I believe there are other cycling itinerary books on the market.
By far the greatest resource was the bike shop we rented our bikes from (no, didn't ship mine). The fact that we were renting something from them gave us an in, but I think that if you could locate French bike shops on your route you could probably just ask for some advice, on the order of, What's the nicest ride to ---, where's a good stop for lunch, that sort of thing.
My other thought is that just because you can ride 60 miles each day doesn't necessarily mean that you should; you might have a better trip with less time in the saddle and more in cafes and caves and chateaux. Up to you obviously, have a great trip!
did a biking tour a few years ago in the south with some friends. Get the Michelin maps that are the highest scale so that you can find the local roads with less traffic.
And don't be in a rush; back in the day I could ride centuries here in CA, but that isn't what you want to do on a bike tour in France. Give yourself time for enjoying the magic of bike travel; pull over to admire a view, stop for a farmers market, visit an antique shop. What we did was pick a base to stay for 2-4 days (on a 16 day trip). On 2-3 days we'd ride out and back, on the other we'd go see local attractions such as the glaciers (this was on a trip in the Alpes) or rest in town. But that's just my opinion; maybe you want to rack up the miles on pretty roads in France.
Since you mention a tandem, you might want to read the blog at http://piaw.blogspot.com/ This is a guy in the Bay area who's done a number of trips in Europe on a tandem so you might pick up some tips.