I've been test riding the Paper Bicycle for the past month, and as I've mentioned before it is a single speed. The gearing is pretty low: 38x17t, with 26x2.5" tires (about 60 gear inches). The bicycle is upright and it weighs around 37lb. Reading these specs, it would appear that the manufacturer geared the bike low to compensate for its weight and upright positioning, enabling the urban cyclist to handle hilly areas. In turn, it stands to reason that the bike cannot go very fast, assuming that one does not want to spin like mad while commuting: a sedate urban bike, where the single speed aims to make the uphill portion of the ride easy and assumes you will coast downhill.
However, my experience of actually riding the bike contradicts this. While the gearing is low enough to handle reasonable uphill stretches, I can also pedal downhill much of the time, and on flats I can pick up quite a bit of speed. Based on what I understand about single speed gearing, that seems implausible, and yet that's how it is.
This is not the first time I've noticed that the single speed drivetrains on some bikes can feel more "versatile" than multi-speed hubs on other bicycles I have ridden, in the sense that a single gear on Bike A can feel acceptable over a broader range of terrain than an entire 7-8 gear range on Bike B. The first time I felt this was when switching between the multi-speed Pashley and the single speed Motobecane mixte conversion, both of which I owned in 2009-2010. The Motobecane was easier uphill and faster downhill, whereas the Pashley's gears would max out in both directions. At the time I attributed this to the city bike vs roadish bike difference, but I have since experienced the same effect on bikes that were more comparable. For instance, when I test rode the Breezer Uptown, I arrived on the Paper Bicycle, then rode the 8-speed Breezer over the same terrain. I had to switch between the high and low gears of the Breezer's 8-speed range constantly in order to make the bike "move" as comfortably as the Paper Bicycle moved in its single gear. It was a poignant contrast, given that the weight and upright positioning of the two bikes are comparable. Others have reported similar experiences - discovering a single speed that was able to cover their commute as well as a multi-speed bike, but without the hassle of constantly switching gears. A single speed Abici has proven sufficient for Trisha of Let's Go Ride a Bike in Nashville, more so than her other, geared city bike.
Increasingly, there is a trend to put 7-8 speed hubs on city bikes. Some beginner cyclists I've spoken to won't even consider 3-speed hubs, let alone single speeds. They do not have exceptionally long or hilly commutes, but after test riding a couple of bikes they feel that multiple gears are necessary. It makes me wonder whether there is something about the way many new bikes are designed, that they simply do not respond well to the rider's pedaling effort and need all those gears to compensate. Is single speed versatility the flip side of the coin to hub inefficiency, or is it all about the frame design? I am far from having an answer, but this seems worth investigating. A single speed bike is easier to maintain and put together, and it is less expensive. If it's possible to design one that can handle mildly hilly terrain, why bother with multi-speed hubs and gear shifters?