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Mid-project test run

June 20, 2011

I’ve been riding the bike for a week since I did a little maintenance on it. Even after only a little TLC it rides much smoother. The lack of a rubbing derailleur on the chainwheel really helps.

Testing gear ratios

A good reason to pause and not completely dismantle the bike immediately is that a) I can still get to work and b) I can test the gear ratio that suits my ride the best. I used to ride with a ratio of 40:15 (or when I wanted to be lazy, 40:17), and so I first calculated the equivalent gearing when using the larger, 52 tooth, chainwheel, which I plan to keep in my conversion. (Note, this ratio measurement does not take into account different sized cranks or wheels between bikes, but since I plan to keep the same cranks and wheels on my bike, the ratio calculation is sufficient. If I needed to change the cranks or the wheel size, I will need to use a method that takes this into account: a useful article and calculator for gearing ratios is found here). This turned out to be a gear I didn’t have – 19.5. However, I do have 19 and 21, so I tested these combinations on the rides. I’ve been switching between a 52:19 and 52:21 depending on how much effort I can be bothered to put in. I think the 52:19 has the most going for it though, it just requires me to try harder!

Consequences for the design

From further research, it seems that the freewheels I will be able to find easily range from 13 teeth to 18 teeth. Since that would give me quite a high ratio, I might have to go back to using the smaller chainwheel in combination with a smaller freewheel.

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