I suppose it really depends on where you are. I recently was in a race and we were cruising at 32 MPH on a flat paved road (on MTBS - not drafting). Coming down a big mountain road decent on my MTB here locally I frequently break 45MPH. On trails it really depends on the terrain. There are some super techy trails where I average 6 MPH and some singletrack race courses where I average 15MPH.