Originally Posted by thebulls
The most useful reply you've gotten so far is the advice to go out and do a test ride and to get narrower, slick 26" tires. Given that you haven't told us the terrain you'll be riding, the estimated times people have posted so far seem highly optimistic about how fast the "average" person can ride that distance on a road bike, let alone a mountain bike.
+1. I just finished a 200 km ride this past weekend and my friend and I took much longer than expected! She's very fast so she could probably have finished much earlier but I'm an "average" rider...I can do very long distances but not very fast.
Our route was pretty flat but we faced a strong headwind for quite a bit of the distance. Coming back it helped some but we checked my friend's Garmin numbers the next day and that tailwind was half the strength of the headwind. @#$%