I hit 47mph ~78KPH a few weeks ago drafting behind a moving truck (not reccomended). I was able to hold that speed for only 3 miles, I was spent! I spun out at 158 rpm (52 / 13). I also over shot my turn off by a block and a half, i couldnt get the bike to slow down!

All time top speed was 58mph, coming down american fork canyon with a stiff tail wind.