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Traveling Will & Robin

Current travels: Three months in the wilderness of Siberia, Mongolia, and the South Pacific

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Sun
5
Sep '10

On Gear and Gears

Yo, MTV, let’s rap! A few different people have asked about the gear that is carrying me across the country, and since it’s all gotten me this far successfully I figured I’d share.

The Gear

My cross-country touring gear, left side

My cross-country touring gear, right side

A few notes: I originally carried an MSR Whisperlite International stove with a separate cookset. and carried the ubiquitous red aluminum fuel bottle on the bottom of my down-tube where the reserve water now sits. My thinking was that white gas would be hard to come by in the desert, so I should have a stove that could fall back to using gasoline. I learned that I cooked infrequently enough that my gas lasted easily through the heart of the desert, so I switched to a canister-based JetBoil. After a few more months, though, I’ve realized that I could do without any cookset: most of the time I either eat cold food or I eat out; next time I’d save the weight and go without. I also am over-prepared, which is my nature. I could definitely save some weight by carrying less: bike repair equipment; first aid stuff; spare batteries; miscellaneous useful stuff (I have a ziploc bag containing paracord, duct tape, a sharpie, zip ties, velcro ties, and super glue), clothes (2 off-bike shirts?), and food (I try to carry at least one full day’s worth of food, but then crave something different when I get to a town, so my reserves just stick around). But, each one of those is hard to give up. Also, for those who wonder: the bike (w/ racks, pump, empty bottles, and helmet) weighs 37 pounds. The four panniers, with a light food load, weigh 46 pounds.

The Gears

I’m riding a 2009 Novara Randonee, REI’s house brand touring bike, and it’s been absolutely great to me thus far. It required one major change, however — it’s gears. While it’s a wonderfully-designed touring bike, no one actually sells a bicycle that is geared for fully-loaded tours across the Rockies.

A quick explanation of gear ratios. The Randonee comes equipped with 48/36/26 chainrings — that is, the biggest cog attached to the pedal has 48 teeth, and the smallest has 26 — and an 11-32 cassette — of the 9 cogs in the back, the smallest has 11 teeth and the largest has 32. Simple enough, right? Now throw in a little math: my tires are 700mm in diameter (about 27.5 inches), which means that for every revolution of the wheel, I go 2.2 meters. If the front and back back cogs had exactly the same number of teeth (1:1) that’s exactly how far I’d go with each revolution of the pedal. Simple, right? But, of course, If the pedal’s cog is twice as big as the wheel’s cog (2:1), the wheel will spin twice for each pedal revolution, and I go 4.4 meters. Since the size of the wheel matters here, the useful number is gear-inches: with a 4:1 ratio, it’s exactly the same as if I had a direct-drive bike (like one of those old penny farthings) with a giant wheel four times as big, or (4 x 27.5) 110 gear-inches.

Combining all the different gear combinations (3 front gears horizontally, 9 rear gears vertically), this is what my bike’s gearing looked like when I bought it, expressed in gear-inches. Again, this is the size of the (giant or tiny) direct-drive wheel it’d feel like I’m pedaling:

117.8 88.4 63.8
108.0 81.0 58.5
92.6 69.4 50.1
81.0 60.8 43.9
72.0 54.0 39.0
61.7 46.3 33.4
54.0 40.5 29.2
46.3 34.7 25.1
40.5 30.4 21.9

I replaced both sets of gears to give me a lower bottom-end, even better suited to very very slowly carrying me and my heavy load up steep mountains. My new setup is 42/32/22 teeth in front, and 11-34 teeth in the back. This gives me my new gearing:

103.1 78.5 54.0
87.2 66.5 45.7
75.6 57.6 39.6
66.7 50.8 34.9
56.7 43.2 29.7
49.3 37.6 25.8
43.6 33.2 22.8
37.8 28.8 19.8
33.4 25.4 17.5

This gearing is pretty “crazy low”, but that’s good; while the difference between 21.9 and 17.5 gear-inches doesn’t seem that big on paper, it’s still 20% lower and makes a big difference when trying to move 250+ lbs of bike+biker up a mountain. The fact that I lowered my “top-end”, meaning that I can’t get as fast of a top speed, doesn’t affect me that much; when in my new highest gear (103 g.i.) pedaling stops accelerating me downhill after about 35 mph, but who cares? That’s plenty fast to get where I’m going.

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