What a difference wheels and tires can make. I recently added a set of Rolf wheels and mounted Durano 20 x 1.10 tires and I mounted them Tubeless for less rolling resistance.

I rode the same route that I did last fall when I started this thread. I was in better shape then. However today I was 1:50 faster at 15:19 when my best time on my 700c bike was 17.10.

I now need a bigger gear on my Dahon. I was spun out probably 20% of the time, not just downhill like i was with the fatter tires and original wheels.