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how to calculate gearing?(4 posts)

how to calculate gearing?gsxrawd
Jun 8, 2002 10:45 PM
let's say i have a big ring at 53 and the small cog at 12, is it 53 divided by 12 times 27 (for 700c wheels)? what about if I have 650c wheels? do I times it by 26?
gear inches...C-40
Jun 9, 2002 4:43 AM
Your forumula is correct (ring/cog x 27), but the gear- inch formula does not give a value that means anything. It's just a gear ratio times a constant.

If you want to compare a 650c wheel to a 700c, you need to know the diameter of each tire. Then take the ratio of the 650 tire diameter divided by the 700 tire diameter to get an equivalent gear-inch value.

For all practical purposes, a 650c bike would use a cassette with a one-tooth smaller top cog and a two-tooth smaller big cog to be geared close to the same (an 11-21 instead of a 12-23).
Yup nmthe dad
Jun 9, 2002 7:30 AM
re: how to calculate gearing?shortstroke
Jun 11, 2002 8:09 PM
Save you the trouble, try this link...