I went on a solo 112 mile ride, went along the coast, over some hills, bike path, city street, open road. I managed 17.5 mph over that distance, went from 17.2 at 90 miles to 17.5 finishing. I wasn't in a hurry nor racing. I did this on a 2008 Fuji Cross Comp with 700x30c knobby tires, into a headwind for the first 90 miles. Lots of fun. Does that give you an average?