When I did the 160 mile RAIN ride, I ate more carbs than usual the whole week before to up my glycogen stores, as Rebecca said above. The night before, I ate a light meal to not feel bloated and full. I had my on-bike nutrition figured out, eating about 200 - 300 calories per hour, a combination of carbs and protein with a little fat (peanut butter) and I started eating that around 5am for a 7am start. I usually ride about 200 miles a week and that week I rode only 100 or so miles Mon - Wed (not high intensity), leaving two full days of recovery (I did an easy walk on Thursday and Friday was no activity at all) before Saturday event. This worked out very well for me - and each person has to find what works best for themselves. Good luck on your ride!!!
The bicycle has done more for the emancipation of women than anything else in the world. ~ Susan B. Anthony