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A Closeup Understanding of Gearinches
Here is a look at what a gearinch really is. I saw this highwheeler at the Dickens festival the end of February in downtown Riverside. Just for comparison my Serotta with a 52 tooth ring in front and 11 in the back would equate to 127 gear inches or a high-wheeler with a 10 foot diameter wheel!
Gear Inches:
One of the three comprehensive systems for numbering the gear values for bicycle gears. It is the equivalent diameter of the drive wheel on 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 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.
Courtesy of Sheldon Brown's excellent website www.sheldonbrown.com/gloss_g.html#gearinch
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