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Keeping it simple: some tips on building your first singlespeed
In recent years, single speed bicycles have been labelled everything from a revolution to a fad, even though the format keeps growing in popularity. There isn’t a specific reason for the fondness many riders have for singlespeeds, but the challenge of riding a bike with limited gearing, its minimalist style, and the ease of maintenance all play a role in its success.
Frankly, all three of the points mentioned above brought me to build a single speed bike this summer. In this article I’m going to give some basic information which can make the task of building a single from scratch, or converting a geared bike into a singlespeed, much easier.
The advantages (and disadvantages) or singlespeeds
PCs vs. Macs. I’ve heard some people talk about singles and standards the way computer folk talk about PCs and Macs. In the same way that a Mac finds a new network and connects without you noticing, the single speed just works. Without the equipment required for shifting, not to mention the rings themselves, a single speed is generally lighter and easier to maintain than a geared bike.
Lean and mean. The trimmed-down, ‘clean’ look of a single speed is also more attractive to many people and I think they just look faster. The downside is that your mechanical advantage for powering the vehicle is limited to one ratio. This has the effects of making hills taller, momentum more precious, and your top speed a noticeable function of your maximum cadence.
Specific parts selection. As for single speed drivetrains themselves they are a surprisingly exclusive breed. Going into this project I was under the impression that much of the technology was “cross platform” and that I could use stuff from my store of spare multi-gear parts to save money. What I ended up with was a brand new drivetrain all together. Those of you converting a geared bike however needn’t loose heart, it is possible to replace only the necessary components, but you might see a shorter life for those that you jimmy-rig.
Choosing a singlespeed frame
The first thing that I discovered is that there are, in fact, singlespeed frames. Although a standard frame can be used (as I did and will explain about) a single speed frame is preferable.
They come in mountain and road varieties and the only difference between them and a standard frame is the rear dropouts. These function horizontally instead of vertically (i.e. the rear axle slides back and forth, parallel with the ground, instead of upward into the frame).
The reason for this is chain length. When you give it some thought you will realise that a chainline has fixed intervals in which it will properly engage the teeth on a set of sprockets at x ratio. Therefore the horizontal dropouts allow the rear wheel and the cog to be positioned where they hold the chain tight. For those of you who can’t find a desirable single speed frame, a tensioner will be required.
If you don’t have a singlespeed-specific frame, you’ll need a tensioner to keep the chain on your cog.
The tensioner is a single-cog arm that attaches to the rear derailleur hanger and is spring-loaded to take the slack our of the chain. In this way you can approximate the chain length (on the long side) and then have the tensioner keep the chain taught.
Choosing your gearing
Once you have your frame situation sorted out it is time to choose a gear ratio. This is probably the hardest part about making up a single speed and experimentation is required.
You need to look at the type of riding you’ll be doing and decide if you want the bike to have more speed or more torque. If you’re like me and plan to use your single on the road in town, then you probably want a ratio which will allow you a higher top speed. It’s important to remember though that you’ll be pushing this ring off stoplights and up hills so don’t go too crazy.
On the road. I enjoy the gearing on mine (46t:16t). Having stronger legs than most, this is a fine setup for me, and it can get me to about 35 km/hr comfortably. I also chose this ratio because, over time, simply riding this setup will be a part of my strength-training regimen. If you’re not interested in that aspect of the singlespeed, you might be better off sticking with a slightly more reasonable 44t:16t setup. This ratio will give you the feel of the “big ring” on a standard mountain bike.
On the trail. For off road riding however you will want a much lower ratio. Most riders will want to go with the equivalent of their “middle ring” up front (36t) and perhaps 16t or even 18t in the rear. This will give you the torque needed to get over gnarly roots while not being too tough in the suck. In the end the only test is to ride it. If you can do the work yourself a good LBS might loan you the rings to try our different setups, or you can get them to tweak it for you. A general rule is that the closer you get to a 1:1 ratio, the more torque you’re going to have, while decreasing your rear will generally increase your top speed. It sounds more complicated on paper then it is in the shop. Just looking at the rings will give you an idea.
Odds and ends
Cranksets. When building up my singlespeed, I made use of a three-ring crankset by putting the single sprocket on the “big ring” holes. Using your old three-ring crank arm allows you to move the single ring up front and establish and straight chainline, so its not a bad idea to go this route on your first bike.
Wheel conversion kits. Another thing that’s important for people doing conversions is to give some thought to your wheels. A rear wheel designed for a cassette can be used but you’ll have to look into a conversion kit that comes with spacers for the freewheel body, a lockring, and usually two or three cogs to try out (see picture above).
This is the route I went with mine since I had a decent standard wheelset lying around. The spacers work like headset spacers and allow you to change where the cog sits. When you get that together you can play around with the spacers to make the chainline as straight as possible.
Chains. Finally, there is in fact a specialized type of chain for single speed drive trains. These are narrower and are designed with durability in mind.
To sum up
All that said, I have found single speed riding fun and challenging. Anyone who is looking for something new or is tired of realigning their rear derailleur should give it a try. Singlespeeds also make great winter bikes, since they are so easy to clean and take apart.
Good luck to all of you putting together your new rides!
1. Posted by Ryan | 12:56 pm, 17 July 2006
Great article. Thanks!