Cycle Sense the chainwheel in use. Count up the teeth of the rear cog in use. Divide the chainweel by the cog. Then multiply that Gearing 101 number by the rear wheel diameter. (Don’t bother measur- ing your exact wheel diameter. It’s customary to round off Let’s start with the jargon to 27 inches for a road bike or 26 inches for a mountain bike.) Then round this number off to the nearest integer, just By John Schubert to keep things simple. Your bike probably has two or three chainwheels and anywhere from five to 10 cogs. (Every combination of few months ago, I went to buy my son skis for chainwheel and cog is a possible gear for your long division Christmas. The store clerks showed me several work. skis, and then so completely baffled me with Some of you will already have dashed out to your their clumsy attempts to describe the differences garage, and made a little chart of the gearing on your Athat I did what any right-thinking parent would do: I got the bike(s). A gear chart can be quite handy for correlating the kid a stereo instead. numbers we’re talking about to the shift lever positions on The experience was a reminder: it can be frustrating to your bike. learn a new activity. Your questions are met with jargon Here is a gear chart showing gear inches for all the gear- meant to impress, or well-meaning explanations by people ing combinations on a Bruce Gordon “Basic Loaded Tour- who don’t know how to explain stuff very well. ing” bike with 26-inch wheels. The chainwheels are 22, 32 So when I got a batch of letters from Adventure Cycling and 44 teeth (across the top row) and the cogs are from 11 to 32 (down the left column): members asking basic gearing questions, I was reminded of 22 32 44 the simple truth: the vast majority of U.S. people, including 11 52 76 104 elite Ivy League graduates, doctors, lawyers and even econ- Charts like this are a veritable 12 48 69 95 omists, do not know the jargon of bicycle gearing. Rosetta Stone to some folks. They help 14 41 59 82 Therefore, you understand gearing so well that 16 36 52 72 today I’m going you can’t wait to type your own chart 18 32 46 64 to bring you up and tape it to your handlebar stem. 21 27 40 54 to speed on what These same charts are anathama to 24 24 35 48 the terminology some others, who dread having their 28 20 30 41 means. overly helpful spouse explain the stupid 32 18 26 36 Bicycle gearing chart one more time. It’s all about dif- is expressed in a ferent learning styles. single number I don’t care which group you fall into, but I do care that called “gear inch- you understand the concept behind the chart so that you can es.” Gear inches (a) answer your own questions about gearing and (b) shift is usually a two- your bike fluently so you’re always in the best gear for the digit integer, and next pedal stroke. the useful range Now you need to know how to set the gear-inch num- of gear inches is, bers in perspective. Here’s my list of approximate uses: roughly speak- 18 to 25 gear inches: steep uphills with touring gear. 25 to 30 gear inches: steep uphills unloaded. PHOTO BYPHOTO GREG SIPLE ing, anywhere from 15 to 120. 30 to 40 gear inches: moderately steep hills. The concept of gear inches dates back to “ordinary” or 40 to 50 gear inches: moderate hills “high wheeler” bikes. Those bikes were sold by wheel 50 to 60 gear inches: mild hills We all diameter, and the larger the diameter of the big wheel, the 60 to 70 gear inches: very slight hills remember farther you’d travel with each turn of the pedals. 70 to 80 gear inches: flats why gearing 80 to 90 gear inches: downhills is so impor- Then came the “safety” bike with its two smaller wheels, tant to tour- and now the wheel diameter sounded like it would slow you 90 to 100 gear inches: steep downhills ing cyclists, down. If you were accustomed to the speed of a 45-inch 100 to 110 gear inches: very steep downhills don’t we? ordinary, a 25-inch wheel would sound something of a over 110 gear inches: warning: gears like this are haz- bringdown. ardous to your knees. So the makers of safety bikes responded by reminding People often ask whether a particular bike has good the customer that their bikes had gearing. For example, a gearing for touring. The Bruce Gordon bike I mentioned 27-inch wheel diameter bike with a 2:1 gear ratio would above is about as good as it gets. The gears are closely take the rider as far on each pedal stroke as an ordinary with spaced together, so you aren’t left wishing for an in-between a 54-inch wheel diameter and 1:1 gearing. They said the gear. (Well, the gap between the 12- and 14-tooth cogs is a bike had 54 gear inches. bit big. That is this gearing’s only significant deviation from This is the nomenclature that survives with us today. the ideal.) The low gear is plenty low enough and the high So every time you want to know the gear inches of a gear is plenty high enough. You can do most of your riding particular gear, you do long division. Count up the teeth on on either the middle or large chainwheel, reserving the Adventure Cyclist • March 2002 small chainwheel for genuinely big hills. The gearing on Sadly, if you buy a less-expensive pro- the Bruce Gor- duction touring bike, you probably won’t don BLT (basic get gearing as good as the Bruce Gordon’s. loaded touring) You’ll probably get chainwheels of features a low gear of 18 inch- 30/42/52 and an 11-26 cog cassette. This es — perfect gives you a not-low-enough low gear of 31 for tackling gear inches and a wreck-your-knees high those mountain gear of 128 inches. For real touring, you’ll passes. want to swap the small chainwheel for a 26- tooth, and you may also want to swap the rear cog cassette for one with a larger cog (depending on what your rear derailleur can BYPHOTO JOHN SCHUBERT handle). If you can get rid of the knee-bust- ing high gear in the process, so much the gears, evenly spaced gears, and a wide better. range of gears. And you don’t need more I believe gears above 90 to 95 inches are than five rear cogs to do that. Every time of very limited use for loaded touring. I like you want the next-higher or next-lower speed, but touring is much better without gear, you double-shift, using both the front undue emphasis on speed. and rear derailleurs. The granny chainwheel For loaded touring, your lowest gear isn’t used in the half-step pattern. You use should be, oh, 18 to 25 inches. the granny chainwheel for three or four low Next question: what should the gaps gears. PHOTO BYPHOTO JOHN SCHUBERT between gears be? My answer, which not Check out this example of five-cog half- everyone agrees with: smaller than they step (gear inches calculated for 27-inch usually are. Ideally, your gears would be tires). This setup shifted well and had great about ten percent apart from each other. gearing, with components sold 40 years How important this is depends on the kind ago: of riding you’re doing. 26 45 50 Tourists riding loaded bikes on long, 14 50 87 96 constant grades benefit greatly from closely 17 41 71 79 spaced gears (and the technique to use Half Step 21 33 58 64 them). When the grade is constant, you’ll 26 27 47 52 settle into a groove, and if you can make The Gearing of Choice for 32 22 38 42 minor adjustments in your gearing, you’ll the Retrogrouch ride better. My circa-1983 Specialized Sequoia, a When you ride on terrain where the light touring bike which I bought used in grade changes constantly, you’re less likely I’ve been silent on Half Step for decades, for one simple reason: you can’t 1991, has six-cog half-step. Here are its to ever get a chance to settle into such a numbers: groove. Under these conditions, gears buy it anymore. And I don’t like to send spaced 15 or 20 percent apart are okay. readers on scavenger hunts for obsolete 30 46 50 How do these theoretical requirements equipment. 14 58 89 96 square with what’s mechanically possible, But we retrogrouches love Half Step 16 51 78 84 or commercially available? The answers are gearing, which dates our bikes to the mid- 18 45 69 75 “pretty well” and “well, okay.” In this era of 1980s or before. And I often get asked what 21 39 59 64 nine-cog rear ends, that’s enough sprockets Half Step is. 25 32 50 54 to have the gears well spaced and cover an Half Step gearing means this: 30 27 41 45 adequate range. But it doesn’t always work You have evenly spaced gearing steps that way, because several of those cogs are between your rear cog teeth.