Posted by Dan O on November 29, 2000 at 10:07:00:

In Reply to: Can someone help me? posted by Alwyn Spencer on November 27, 2000 at 11:49:06:

Notwithstanding you know the mechanism of the derailleur

is to simply select between the gears, the issue the mechanism

affects is the final ratio of the number of times the wheel goes

around beyond compared to the number of times the pedal crank

goes around is strictly the ratio of the numbers of teeth on

the front sprocket to the number of teeth on the rear sprocket,

so you divide one by the other. Depending on which ratio you

wish to express, crank turns per wheel revolution, or revolutions

per crank turns, you put either the front or the back sprocket

in the numerator of the fraction. example: 20t front 40t back.

ratio of wheel turns to crank turn is 2:1 (40/20 reduced to lowest

terms), ratio of crank turns to wheel turn is 1:2,

(20/40 reduced to lowest terms). Gear ratio is nothing other

than considering numbers of respective teeth.

- Re: Can someone help me?
**Alwyn Spencer***12/01/00*(0)