I usually take 51 minutes 28 seconds to 52 minutes to commute 20 km using my singlespeed Dahon geared at 62 gear inches from door-to-door with or without the fairing. Pics of the setup here.

To test the theory that I should be faster using gears, I put back gears (SRAM 8 speeds) on the bike, lengthened the chain and tuned it up again. I even have more aerodynamic trekking bars that allow me to crouch into a more streamlined position. The idea behind gears is that I can go spin uphill and go faster downhill and faster on the flats. So I cycled with the same commitment I usually do today.

Today's time? 55 minutes 12 seconds. Longer time by 7%. My average speed went from 23.3 km/h to 21.7 km/h. I don't understand. I really wanted this to work. I was faster without multiple gears and using just a flat bar with bar ends.

If you know Vancouver, my commute is from west Richmond by the dike, to River Rock Casino, across the CanadaLine bicycle bridge, north on Cambie Street from Kent Ave all the way into downtown (huge uphill all the way), right to Waterfront Center or Sinclair Center at Howe and Cordova.

Why was I slower? I rode just as hard as I normally do.