I just finished a 160 miler in around 9 hrs. I do a couple to three big rides like this every year. My training consist of increased milage every week. Be sure to take a day off the bike and at least one day easy spinning each week. The weekend before the big ride I try to do a ride that is > 60% but < 75% of the big ride. For the rest of the week leading up to the big day I eat 20% more good carbs than normal, drink water all day long and increase my sodium intake. I ride only a few days the week before but very easy and lay off completely two days before the big event. When I don't ride I usually walk the neighborhood just to stay loose. (no need becoming a couch potatoe). Take your vitamins and get more sleep than usual. Night before eat a moderate meal with plenty of good carbs such as rice, oatmeal, potatoes, pasta topped off with some grilled chicken (no steak and fries) and fresh fruit. Just before bed eat some cottage cheese and fruit. I eat a bagel with peanut butter for breakfast and sometimes oatmeal and wheat toast about 2 hrs before the event. Pop a bananna or two before start and you arre set. If you have the base miles and eat right you will be fine.

Base miles are real important as well as hydration, rest and nutrition.

Things NOT to do.

No diet pop, tea, or other diaretics a couple weeks out. Especially none the day off or before.

No fast food or heavy meals with greasy stuff.

you are thinking right when you think preperation. Those who don't suffer. I have done this for a while now and preperation pays big dividens.

There is more - I am just tired of typing.

Good Luck.