Well i've achieved 45.5 mph believe it or not rocketing along a smooth road with a very slight rise to it in Birmingham (England) city centre. Felt unbelievably exhilarating..i was almost spinning out on a 53/12..i actually passed a few cars..the looks on the drivers faces certainly told a story..they looked horrified !..one of my favourite cycling memories..Never reached anywhere near this speed since except on downhills of course.