The first group road ride I was on (on my fuji road bike) I did 44miles in a little over 2 hours, more like 2 1/2. I'm probably in the same shape now, but I've been wanting to get out and jog over the break to get my endurance up.
After reading your post I am still not sure what kind of trail you are planning to ride on this 50 mile venture. Is it hilly? What is the surface like? I think what you have stated here is that you rode a Mountain Bike for 44 miles at some point in time, in 2.5 hours. That is 17.6 mph based on my calculations.
If you ever averaged that speed for 2.5 hours off of pavement, you accomplished quite a feat. Sounds like you are up for it. I have ridden nearly 7000 miles (= to across the U.S and back) in the last 13 months on mainly unpaved roads. I have never averaged that speed for 1 hour, let alone two and a half. I also consider myself in pretty good shape. At least up till now.
