I can’t imagine anyone getting out a gear calculator to find their gear. But having arrived at their preferred gear I can image using a gear calculator to keep that gear (or something close to it), especially when changing parts like I did recently.
Fixie Buddy and and Fixed Gears are two Android apps that do the job of calculating gear ratios for you.
 |
| Fixie Buddy has a pretty simple interface. |
For example, here are the ratios for two of my bikes according to Fixie Buddy:
42 tooth front + 16 tooth rear = 2.63
38 tooth front + 16 tooth rear = 2.38
Not much difference on paper but a vast difference when riding. The second bike is the bike I choose when I have to plough directly into one of the GCs cruel southerlies. I spin out on the way home of course.
So far there’s nothing particularly tricky about what this app does for you. Pull out a calculator, and divide 42 by 16 and you’ll get 2.63. What Fixie Buddy also tells you is gear development, how far the bike will travel with one revolution, and this takes into account the size of the rear tyre also.
42t + 16t + 28 tyre = 6.1 metres
38t + 16t + 23 tyre = 4.98 metres
And there you can really start to see the difference between the two bikes. Every time I turn the pedals the first bike goes a metre further than the second bike.
Interestingly, the Fixed Gears app gives slightly different results. Over there my development is 5.7 metres. You have to move in and out of menus a bit more with Fixed Gears but it has two advantages, one it remembers your previous measurements and two it has an Alternate Gearing option. This would be great if you had to change, say, a rear cog because the one you had is an odd size and not available (like my 16 tooth rear was) or because your mate gives you a perfectly good 48 tooth front and you want to know what to replace the rear with to get a match. In my case it suggests an 18 tooth rear, which is the combo I used to have.
 |
| Never fear, metric is there also. |
