Originally Posted by
mihlbach
Not exactly. The difference of one tooth on either your cog or ring will move the axle 1/8". For example, subtracting a cog tooth decreases the circumference of the cog by 1/2 inch. The chain only goes half way around so the chain has 1/4" less contact with the cog. That gives you 1/4" of slack. Divide that in half again to account for the upper and lower parts of the chain and you have 1/8".
Mihlbach, he's not talking about going with a smaller cog or ring, he's talking about removing a link from the chain.
The length from center of one roller to the center of the next is 1/2". When you remove a link, you have to remove "two links" - a set of inner and outer plates (unless you cheat with a
half link) - which removes 1" from your chain. That translates into 1/2" from both the top and bottom of the chain (between the chainring and cog), moving your axle 1/2".
Edit: I just realized that bidaci
was also talking about removing a tooth. And your reasoning on that matter seems sound. Amen.