Originally Posted by
dsbrantjr
The cable tension is provided by the spring in the derailleur; it will vary depending upon which gear it has selected; it has more tension the farther you pull it, just like any other spring.
The so-called "tension" adjustment provided by barrel adjusters and the like is actually a cable length adjustment or more accurately a cable housing length adjustment, which sets the relative position of the derailleur vs the shifter index "clicks".
Great feedback! So, say the chain is on the 23 cog, and I turn the adjuster 1/8th of a turn. That 1/8th of a turn should be the same adjustment for the other cogs right? Or does that 1/8th of a turn turn into more/less of a turn further down the cassette due to the spring tension in the RD? Or... am I just overthinking all of this, and I just need to replace my housing? :-p