Running Primo Comets on it.

I ride my Brompton at the same speed as my other bikes, or at least attempt to, it takes more effort, or it seems to. I have had other small wheel bikes in the past, R20, a 64 Moulton /Huffey, Dahon. These also were an upright position. They seemed quicker. It is not that the ride is bad, just more effort.

The only thing I can come up with is is that the rear shock flexing. I have the stiffer one.