S2 Duomatic…

Wow…what fun!

I’ve been riding on my new wheel for a couple of days now and trying to get the hang of my Sturmey Archer S2 Duomatic hub. Basically this is a simple rear hub that gives you 100% and 138% gear ratios. It’s completely self-contained and requires no cabling or shifting mechanism. You just rotate your pedals back a little and voila, the wrong gear.

Okay, not always the wrong gear, after all, there are only two. I just seem to get the wrong one when I try to take off from stop. I’m pretty sure I’ll improve with time. Even now, after just a couple of rides I’m pretty good at shifting while in motion. It’s just the stopping thing that’s got me beat. I think it has to do with the fact that I’ve been shifting down to the straight 100% ratio as I approach a stop. Generally I end up moving the pedals a bit while stopped to get prepared for moving again. That’s where it happens. Perhaps if I just stay in 138% when I stop the small movements will move me down to 100%. Practice, practice, practice.

Why the heck do I need a two speed anyway? I’ll admit I wanted mostly so I had a really good reason to build a wheel. But in fact, it turns out to be a good thing.

I ride single speed bikes around town a lot. I’ve got two; a lovely Rivendell Quickbeam, and my pumpkin orange Fujiyama. The Quickbeam can actually be switched between a variety of chainring and freewheel combinations, though you do have to stop to do it. The Fujiyama however was a pure single speed.

It was okay till I ended up with bursitis in my left hip. At that point I realized it was geared just a touch too high for me. It was fine as long as I was already moving but not so good if I had to take off from stop. Normally I’d just go slow and build up speed, but it was hurting my hip a bit to mash. The solution, gear down a bit. I did. This made it easier to take off but also made it impossible to build up any speed.

My setup had been 26″x2.35″ tires, 175mm cranks, an 18t freewheel, and a 42t chainwheel. That’s about 61.6 gear inches. Not a big problem if your hip is working well. And it’s fine at speed around town. But with a bad hip…not so much.

I switched to a 22t freewheel which was much better for starts and stops at 50.4 inches. Of course there’s not much you can do about speed, but it was better. Still that would be a bit high at 138% higher. So I went with 38t up front and 22t in the back: 45.6. Easy to start and stop but nothing else. Sigh.

Ultimately with my S2 I end up with gear inches of 45.6 in low and 63.0 in high. That’s nice and low for starts and stops and high enough for pedaling around. Yes a bit higher would be good too, but right now, with the hip, low is better. I can easily change the ratio later.

So far so good.

When all is said and done, and my hip feels better, I’ll probably swap the gearing again to get to 52.8 and 72.9 (40/20 front/rear). But until then, my hip thanks me for the lower gearing.

Here’s a little better image:

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