SM> Can someone please explain just what a "gear inch" is and how to 
 SM> measure it?  I know it has something to do with how far the tire 
 SM> moves for a given pedal input but I'm not clear on the details.
 
 BA> It is a reminder of the old "penny farthing" high-wheelers. You 
 BA> calculate the gearing as if you are running a large wheel of that 
 BA> diameter. Assuming you have a wheel diameter of 27 inches, you 
 BA> calculate gear inches by counting teeth in the chain ring and the 
 BA> rear cog, dividing and then multiplying by 27". In other words, you 
 BA> are running a 42T front and a 21T rear, a ratio of 2.0. Multiply 
 BA> that by 27 and you have a "wheel" of 54". 
Dear Barry:
Thanks for the posting.  I got the same answer from somebody else so it 
must be true.  I'm still of the opinion that it would be easier to 
understand if it measured how far the wheel actually rolled on the ground 
for one turn on the pedals in a given gear ratio.  Anyway, at least I 
understand what it is now.
Later,
Steve
... Neighbourhood:  a gangster who lives next to you
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