Bike ≠ Car ≠ Ped.
Join Date: Jul 2007
Location: Washington, DC
Bikes: Some bikes. Hell, they're all the same, ain't they?
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+1 to the above post.
To explain it further, what you'll be doing is taking up the slack in the shift cable, which lets the indexing work correctly.
When you move the shift lever, it pulls a certain amount of cable, but no more. The "click" is basically a ratchet mechanism which regulates the amount of pull. If there's slack in the cable, the shifter has to take it up before the derailleur moves at all. Then, you're left with a portion of the cable pull only taking up slack and not moving the derailleur.
When the derailleur is in the small chainring, you want just enough cable tension so that the shifter can act instantly, but not so much that it holds the derailleur away from the limit screw.