Also make sure you are eating correctly: before and after the race. This includes:

Before:

-Pasta w/light sauce (if you want) the night before to get your glucose levels up
-No or minimal dairy on race day
-Carbs w/a little protein for breakfast
-Water, water, and more water (especially the night before, but remember to go potty before the race)

After:

-MILK. It's one of the best recovery drinks. A fellow member named Carleton has recommended chocolate milk a lot.
-Remember to replace the calories you burned. A 4-5 hour ride with lots of climbs can burn upwards of 4000 calories.

I didn't include everything and some of the stuff I said may be off. Hopefully the people who know what they are talking about with chip in.

/rant.