Originally Posted by alienator .
Yes, absolutely. What happens when you "adjust the indexing" is that you adjust the rear derailleur cable tension, which ultimately aligns the rear derailleur's top pulley with respect to a given cassette cog. If that cable tension is too loose, the chain may have difficulty shifting to the next bigger cassette cog or may shift to the next bigger cog but then skip back to the lower cog under power. If the cable tension is too high, the RD will shift to bigger cogs quickly but will shift to smaller cogs slower than what is ideal. The RD may even skip a cog and go to an even bigger cog if the tension is too high. Sometimes when the adjustment is out of whack and the tension is high enough, you may only get access to 9 out of 10 cogs....or 8 out of 9, depending on the system you have. In both cases--cable tension too high and cable tension too low--you'll most likely hear excessive chain noise while pedaling. No matter the case, the tutorial for making that adjustment on the Park Tool site is about the best available and is also a solid technique.
Quasi related.........you should bookmark the Park Tool site since the site gives tutorials for virtually any adjustment, maintenance, or installation you might do to the bike. All of their tutorials are straight forward and easy to understand. It's a great resource. Believe it or not, another great resource for learning about bike maintenance and repair is YouTube. There are video tutorials for virtually anything you might want to do to your bike. Lastly, you should also bookmark the website for whatever company makes your component group: Shimano, Campagnolo, SRAM, or Microshift. They all will have (at least Campy and Shimano do) all the relevant installation and maintenance instructions (in pdf format) on their website. I keep pdf's for virtually all my bike components on my computer, just in case I incur a head injury and can't remember how to do something or if I need to do something I haven't before.
A couple big bonuses to learning how to work on your bike are that it is of course cheaper than having an LBS do it (shop time in an LBS can be on the order of $50/hr--give or take a couple or more dollars); it can be immensely satisfying; and it makes you more aware of your bike's condition.