Originally Posted by Machka
A flat shouldn't put you in the SAG wagon ... you just need to change the flat and keep moving.
During your preparation for this century, you did learn to do some bicycle maintenance, didn't you?
As for the ride itself, just remember to eat about 250 calories per hour, and drink about one 750 ml bottle of water and/or sports drink every 1 to 1.5 hours.
Ride at a steady, comfortable pace ... not too fast, not too slow.
Don't forget to bring your tools, a jacket, and a few spare energy bars.
http://www.machka.net/century.htm
She knows what she's talking about. If you're a big person you might need to / be able to eat and drink more than 250 calories per hour; I know I do during centuries.
One 50 mile ride? My rule of thumb is two, but it sounds like you're ready anyway. Focus on riding just to the next rest stop if you're feeling a bit beat along the way. A little break can do wonders!