Originally Posted by
DinoShepherd
Gear inches.
How do they work?
- Z
Originally Posted by
Homebrew01
Compacts give you a wider range than a normal double, so they are good in hilly areas. .... maybe you'd like it ?
From the master, Sheldon Brown
http://www.sheldonbrown.com/gain.html
Gear Inches
The simplest system in common use is the "gear inch" system. This dates back to before the invention of the chain-drive bicycle. It originally was the diameter of the drive wheel of a high-wheel bicycle. When chain-drive "safety" bikes came in, the same system was used, multiplying the drive wheel diameter by the sprocket ratio. It is very easy to calculate: the diameter of the drive wheel, times the size of the front sprocket divided by the size of the rear sprocket. This gives a convenient two- or three-digit number. The examples listed above are all around 74-75 inches. The lowest gear on most mountain bikes is around 22-26 inches. The highest gear on road racing bikes is usually around 108-110 inches. Unfortunately, the handwriting is on the wall for all inch-based measurement systems.
and If you grew up when Gear charts regularly referred to gear inches, and we talked about what the low nd high gear of a bike was in gear inches, you know what 38 gear inches feels like, and how low of a gear that is.
Otherwise, it's a totally antiquated way of looking at things, and it's make more sense to think of gain ratios, or better yet mph at a given cadence.