The fastest I ever road was when myself and four other cat 3/4 road 100 miles on a perfectly flat road on the delta region of eastern Arkansas. We went 100 miles from Blytheville to Jonesboro and back in a little over 4 hours in a rotating pace line. Avg speed of 24 mph. We were toast when we finished. On the way back we had a slight tail wind and were hitting speeds of 27 mph.