Originally Posted by Al1943
You've got a good point but in reality it does effect tension because adjusting the derailleur with the barrel adjustor depresses or releases the derailleur spring. If the derailleur is adjusted all of the way to the low limit stop the cable becomes slack. With the derailleur in the big cog position there is more tension on the cable than when it is in the small cog position because the derailleur spring is fully depressed.
Al
It’s more than a good point it’s a hard and fast mechanical fact.
In order to understand how to effectively adjust a thing without tweaking and guessing, trial and error style you must truly understand exactly how a thing works. That is what I was trying to convey to him and now to you.
If you think in terms of tension on the cable you are not understanding the appropriate dynamics. Your attention is being diverted by something that doesn’t matter. As long as there is no slack in the cable the amount of tension is irrelevant, the cable isn't stretchy enough to affect anything. Forget about the tension; just think about the position of the shifter detent first and then that the cage position corresponds to that position over the proper cog.