Mate of mine did Geneva-Nice on a single speed. http://www.chargebikes.com/projects/project/files/pluginthealps/
The trouble with fixed will be the DOWNhills as you'll have to spin like a MF for up to an hour at a time, on the way down those big mountains, while all your freewheeled chums will be coasting at 40mph.
Maybe fit a freewheel, or pay REALLY close attention to your chain tension. You do NOT want the chain to fall off.
Mate of mine did Geneva-Nice on a single speed. http://www.chargebikes.com/projects/project/files/pluginthealps/
The trouble with fixed will be the DOWNhills as you'll have to spin like a MF for up to an hour at a time, on the way down those big mountains, while all your freewheeled chums will be coasting at 40mph.
Maybe fit a freewheel, or pay REALLY close attention to your chain tension. You do NOT want the chain to fall off.