I love a singlespeed bike. A solo chainring connected to a lonely cog via a dead straight chain is a thing of beauty. There’s an elegance to any bicycle, but one rid of derailleurs, cables, wires, and batteries is especially evocative. A singlespeed signals a rider with commitment, one who is willing to eschew the labor-saving devices of the 21st century, and one who certainly rides to the beat of a different drummer.
Because of those feelings and because I just set up a singlespeed for winter training, I wanted to take you through the process of building, or perhaps deconstructing, a single speed gravel bike and how I select a gear. It’s not a complicated affair. With a little attention and some research it can actually be straightforward.
First off is deciding on the bike. In my case, I took one of my geared bikes, my Black Mountain Cycles Monster Cross. Because it has horizontal dropouts it is an obvious candidate. I don’t need a chain tensioner from Surly or Paul Component to get it done, just a good chainline and a secure quick release (go with Shimano or Paul internal cam models), a Paul in this case. I took off the shifters, derailleurs, cables and chain. I then installed a pair of non-brifter brake levers on a pair of wider Salsa Cowchipper handlebars (nice for extra leverage). Then I went about figuring a gear combination to run.
I learned about gear inches in my junior road racing days thanks to gear restrictions and also thanks to my limited time on the track. I know from previous experience that gear ranging from 62.5 to 64.0 gear inches (the distance I’ll travel for a complete revolution of the cranks) works for me when gravel racing on rolling terrain. On the Black Mountain Cycles I can run tires up to 50mm in width with ease but I plan on mostly using 42mm tires. So I set on a 42 x 19 ratio which with 700 x 42mm tires works out to 61.4 gear inches. That’s a little undergeared on purpose. First of all I live at altitude and those race gears were closer to sea level. Secondly, I wanted something a little smaller to work on cadence and open up the possibilities of longer climbs as well.
If you don’t have any frame of reference for gear inches though, a practical way to learn single speed gearing is to examine speed for a given cadence. Both BikeCalc.com and Sheldon Brown’s gear calculator can help. For example, I’m happy riding at or just above 90 rpm on a geared bike. It’s my happy place cadence. Sure I can and do go higher and on steep inclines I certainly go lower, but it’s a typical average cadence for me. On a single speed though, your average cadence will be lower. Knowing that, I’ll have a think about the terrain I’ll be encountering and the average speed I’d like to maintain.
So let’s say that I want to average 15 miles per hour and 80 rpm at Land Run riding 700 x 32mm tires (I use this example because it’s what I did at Land Run this year. For more head here.). I know the terrain is rolling, but without any sustained (by Colorado standards) climbs or descents. (The mud can be an issue though and if it looks like rain, I would opt for an easier gear.) A 40 x 17 with 700 x 33mm tires gives me a 63.5-inch gear and at 80 rpm, that’s 15.11 miles per hour. Presto!
Once you build up or acquire a singlespeed, I encourage you to take notes. Once you have some time on a given gear, be sure you jot down what you’ve used and how it worked for you. For instance, I’ve ridden Dirty Kanza 200 on 42 x 19 with 29 x 2.0” tires. That’s just under 63 gear inches. Because of the extra distance and lower average speeds I geared down a tad. These are useful references for me because I can also recall the conditions (dry at DK that year and at Land Run this year) and even look back to my records of the day and my fitness at the time (I use Training Peaks for my personal training and to coach my gravel athletes).
So while the beauty of singlespeed lies in its simplicity, taking a few extra moments to consider your gearing can help make the experience sublime. That, or at least limit the amount of the time that your one and only gear is the wrong one!