The pigeons have been running grand, albeit I am looking forward to throwing the 25t sprocket on the rear, for a wee bit of extra low-end oooompf. The Sturmey-Archer hub is performing nicely, displaying a very unique ratio curve. You see, the hub has a 1-to-1 1st gear (one revolution of the crank translates into one revelation of the hub gears), but then sees a dramatic jump from 1st to 2nd gear (28% increase). Conversely, 2nd through 7th gears feature small, even jumps (apx. 13% between each gear). While this would be very useful for most typical applications, these gears are still pretty tall compared to a traditional sprocket/derailleur setup, or Shimano Nexus/Alfine, which displays a 1-to-1 ratio in 5th gear. The Shimano hub would offer a more usable range than the SA hub using a more traditional chainring/sprocket combo. Regardless, the SA hub continues to be super-quiet in all gears and when shifted correctly, produces good crisp shifts.

This being said, I may play around with my rear gearing options a bit, at least on one of the tomato twins. I’ve considered the Nuvinci hub, but they are quite strict in demanding a 1-to-2 sprocket/chainring ratio. What’s more, the hub is a bit pricey. I’ve also looked at SRAM’s I-MOTION 9, which offers 9-speeds, an impressive 340% range, and smooth 17% spaces between each gear. But this is also a pricey option. I’d likely prefer the SRAM hub to the Nuvinci due to the fact that I could get lower gears by having a more flexible sprocket/chainring ratio, and the weight is a bit lower overall. Regardless, in my opinion the big elephant in the room is whether to consider a traditional sprocket/derailleur setup.

I like the simplicity of the sprocket/derailleur, as well as the weight benefits and ease of use/maintenance. What’s more, they typically feature a more reasonable cost. But with the Carrier Pigeon, the devil is in the details. If you swap out the internally geared hub for a traditional sprocket/derailleur setup, you lose the drum (roller) brake, which I truly love. The Sturmey-Archer roller brake is solid and performs very nicely, wet or dry, increasing its power very smoothly when applied. It’s not something I’d prefer to lose. Interestingly enough, ridding yourself of the roller brake isn’t really an option as the Carrier Pigeon doesn’t have typical brake mounts on the rear stays. Subsequently, you cannot add cantilever, v-brakes or discs to this bike. So, you could add a sprocket/derailleur setup, but you’d lose your rear brake. I suppose you could just enlist someone to weld-on some brake bosses, if that’s your fancy, but I’d prefer to keep a roller brake in the rear.

Fortunately, I’m not the only one who loves roller brakes. As many folks who own tandems are well aware, most touring tandems are equipped with rear wheels that feature the sprocket/derailleur combo with a roller brake –a big one at that. That’s right, Shimano makes a couple of rear hubs that accommodate the simple, yet beautiful Japanese Arai roller brake, used on tandems primarily as a drag brake for speed control, something necessary to avoid over-heated rims on long descents. The only issue with this setup is that the hub and brake combined place the fully built rear wheel in the same cost category as an internal hub (~$300-$350), albeit with a superior rear wheel build and the world’s finest roller brake, not to mention the flexibility of a wide-range 9-speed cassette. In my opinion, the benefits would outweigh the cost and I may push ahead and try it out.

As a technical side note for those would-be cassette-seekers, the Arai-compatible Shimano rear hub is 145mm wide, requiring the chainstays be spread 5mm on each side to accommodate the hub, so I’ll ensure this is safely doable before pressing ahead. Fortunately, the Carrier Pigeon is high-tensile steel, so this should not be an issue.