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  Gear Inches – archaic system for penny-farthing high wheelers. www.babs.co
  -->Metres Development – metres travelled per pedal revolution.
-->Pedalling Cadence – pedalling r/min x gear selected = speed.
-->Tyre Circumference – an easy way to measure it.
-->Derailleur Gears – simple formula for calculating metres development.
-->Hub Gears – not-so-simple formula for calculating metres development.
-->Gain Ratio – distance bike travels : distance pedals moves.
-->Gear Inches – archaic system for penny-farthing high wheelers.
  BABS.CO » Bicycle Gears Explained » Gear Inches  
Gear Inches…

Penny FarthingChild's TricycleGear inches are part of an endearingly archaic system that works out the size that the bike's driving wheel would be if only the pedals were connected directly to it – as on a child's tricycle or a penny-farthing high wheeler.

The dinky red kiddy trike has a front wheel of fourteen inches—hence, 14 gear inches.

By contrast, the ever-so-macho penny-farthing has a driving wheel five feet high—60 gear inches.

A circus clown's unicycle might have a 20-inch wheel—20 gear inches.


Gear Inch Formula

tyre diameter x chainring / cassette = gear inches

Example A: 48-tooth chainset and 24-tooth rear sprocket:

  • 26in x 48 / 24 = 52 gear inches
  • diameter x chainring / rear sprocket = size of penny-farthing's wheel

Example B: 48-tooth chainset and 16-tooth rear sprocket:

  • 26in x 48 / 16 = 78 gear inches
  • diameter x chainring / rear sprocket = size of penny-farthing's wheel
2013-03-26 19:29
 

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