Decide on a gear ratio for your fixie
The gear ratio of a bike is the ratio of chainwheel to cog teeth. Choosing an appropriate gear ratio for your fixed gear or single speed bike is as important as any other factor to ensure happy riding. The question is often debated in bike forums and the typical answer is that everyone is different and no ratio is right for everyone. Some factors to consider are the terrain and type of riding you intend to do in your area, your fitness level and leg strength, and your preferred cadence.
Starting first with terrain and riding style; if climbing hills is important then you will need to select a lower gear ratio, to make the most of your riding, than if most of your riding is on the flat, where a higher gear ratio will suit better. Remember that, even on the flat, a lower gear will make starting easier and allow for punchier acceleration at the expense of a lower top speed. This may be something to consider in urban areas with a lot of stop-start traffic.
Whilst some seasoned cyclists may profess to riding huge gear ratios, that may not be right for everyone. Fitness plays a part too. Think too about the strain this may place on your knees. It is better to start with a lower ratio and increase later than opting for a knee grinder straight out.
This leads us to cadence. Cadence is a rate, typically expressed as the number of pedal revolutions per minute. Ideal cadence varies between individuals and may depend on your height, sex, and body geometry. Recommended cadences tend to be around 80-120 rpm. Find a gear ratio that allows you to reach your ideal cadence. Bear in mind that sometimes this "ideal" cadence may feel faster that what you are used to. One of the advantages, of fixed gear bikes at least, is that they usually force you to pedal faster than normal.
Technical factors will also influence gear ratio selection. These include crank length, wheel size and bike geometry and you should investigate several ratios until you find a suitable one for your bike.
If you are riding fixed, make sure that the ratio of chainwheel to cog teeth is not a round number, such as 48:16. This will cause uneven tyre wear as a certain crank position will always correspond with the same tyre contact point. If you start, stop or skid with your feet in the same position, then your tyre will wear unevenly. Choosing a different ratio, such as 44:15, will avoid or alleviate this problem as there will now be multiple contact points.
For fixie conversions, that have horizontal or diagonal dropouts instead of track fork ends, a further constraint may be finding a ratio that is compatible with the desired chain length and rear wheel position. Changing the size of the chainwheel and the cog will vary the distance between the bottom bracket and the rear axle for a given chain length, so some consideration is required.
So that gives a brief overview of how to select a gear ratio for your bike. With manufacturers now offering track bikes for the road, the factory gearing is often quite high. Hopefully this article will give you some guidance, whether that ratio is right for you.
Thanks to cyclelicio.us for the photo.
Happy riding!
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For a comparison between
For a comparison between road and track cycling, most Keirin riders race 50x14t or 51x14t, with the largest sanctioned value being 55x12t.
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