Ok, I kind of feel your pain now. I have started my off season training about a month ago and started riding a mountain bike on the road instead of my road bike. Boy have I slowed down. I can hit 20 to 21mph for a few seconds to about 3 minuets at best but after that I slow down, if I want to or not. So I'd work on getting much thinner tires and less tread on them. Also a more aerodynamic position helps the most. I go faster even on the moutain bike if I get closer to the handlebar and lower my profile.

