Plane to train connection time at De Gaulle.

"I would think that the lines might be a little shorter at the end of September,"

No, not in my experience. September is a big tourist month for Paris with lots of conventions and Paris Fashion Week.

I've flown that route from MSP a couple of times and have been lucky enough to have gotten a good tail wind with an early arrival a time or 2 but that's not something you can count on. Deplaning and getting to the Immigration area can often take 15-20 minutes before you actually get to the place where you stand in line for border control.

The 8:48 is really pushing your luck. You have to pray your flight is on time. Then you have to wait to deplane, get through immigration, ?pick up your luggage?, and then get to the TGV station in an hour. Too chancy for me by a long shot.

What lines were you referring to? Immigration lines? Sept is still a big tourist month. It depends on how many other flights are arriving around the same time.

I think your odds would be somewhat better than even that you would make the train, if you carry on your bags and do not have to fetch them from baggage claim.

These are not good odds.

The 12:48 gets you to Rennes by 15:23. I know you do not want to go into Paris, but there is a 10:56 train from Montparnasse that will deliver you to Rennes by 12:24. You can almost certainly make this train.

September is the busiest month in Paris and most expensive for hotels. It is high high season for tourism; if anything immigration may be more stacked up than in August.

The rule of thumb is 3 hours for a train from CDG and 4 from Paris --- you might make this if the plane is early and everything goes smoothly, but there is a fair chance of missing the train. One option is to get very early cheap tickets; these used to be called Prems -- we got them Paris to Bayeux for 15 Euro. If you can get really cheap tickets like this several months out, then you can chance it and just figure on buying full priced tickets for the later train if you don't make it with a philosophical acceptance of the risk.

The easycdg website suggests a minimum time between flight and train of 80 minutes, which you are just under. As Janet said, if you're able to get really cheap advance-purchase tickets that you know you might have to throw away if you're late, then maybe buy tickets for the 08:48. I wouldn't do it, but others might--our differences are what make the world go round, n'est-ce pas?

Forget the 08:48 departure. It may take you 45 minutes or more to clear Immigration and Baggage Claim, assuming you have checked luggage, even if you land on time.

I would take the 12:48 departure. Booking early to get a lower price means you are locked in to that specific dep time and train number, ie you've sacrificed flexibility for savings is what it comes down to.

Thanks so much for all of the replies and suggestions. I think we'll look into the 10:56 train as a backup plan to the 8:48. It would be worth it to get to Rennes sooner, as our final destination is Mont St.-Michel, where we're staying for a few days before heading back to Paris, where we'll be seeing Jimmy Buffett play in Montmartre, at La Cigale.

Parrot-heads in Paris. Who knew?
Hopefully, you're not Viking fans. Stop in at the WOS bar in the Sorbonne area to watch the Packer game.

CDG recommends 80 minutes for an international arrival that has to clear immigration? I am astounded. IN recent years unless I was in business class, it has always taken at least an hour to clear immigration; it would not be unusual for it to take the full 80 minutes. It depends how many jumbo jets land just before you and also how well staffed they are. CDG is notorious for light staffing and long lines.

I have to confess, Sam from Green Bay, that my wife is a Vikings fan and I am a long-suffering Bears fan. We're doing the Friday night show this year. Last year we saw him on Saturday, our first time doing so in Paris. Nothing quite like seeing him in a 900-seat old opera house in Montmartre, after which seeing him in a sports arena is not at all appealing. See you there in September?