cyccommute 

The rubbing and the clicking/popping is one problem…a cable problem. The chain rubbing on itself while in smallest cog is a completely different problem. That problem is a chain length issue.

If the barrel adjuster is out as far as it will go, you should unclamp and retension the cable (not loosen it). Be careful if the barrel adjuster is out as far as it will go as it is easy to disconnect it from the derailer. That will cause shifting problems as well since there is no longer predictable tension on the cable. The cable can flex with the loose barrel adjuster and the derailer won’t work properly.

Okay, you’ve got the problem fixed but only just. Your cable has stretched from the initial installation. Cables do that. They have about a 0.5% construction stretch in them even when prestretched from the factory. That works out to be about 5mm over a 1m long cable. The shifter moves cable in fractions of a mm for a shift so being off by 5mm is a huge amount. You need to release the anchor bolt, screw in your barrel adjuster most of the way, pull up the slack of the cable, and reset the anchor nut. You don’t really need much adjustment to release tension on the screw as most of the adjustment needed will be for cables that are too slack.

When you reanchor the cable, the cable should be taut but not super tight, especially for the rear. It shouldn’t be like a guitar string but you shouldn’t be able to pull it away from the frame much either. You can now make slight adjustments with barrel adjuster. Shimano, in my experience, works best with a little more slack than SRAM. The front derailer cable will be also be tighter than the rear for both.

Finally, once you have most of the construction stretch out of the cable, you won’t experience much more cable adjustment over time. I shorten that initial stretch by pulling the cable up tight and shifting the system without pedaling. I shift 3 to 4 gears a few times and check the cable tautness. It is usually quite slack and I readjust. This significantly decrease the amount of adjustment I need to do.

cyccommute 

Pay little attention to people who tell you that you have to list specifics about your bike. I’ve worked on 15,000 to 20,000 bikes over the last 10 to 15 years at my local co-op. In that time, I’ve seen just about every mechanical derailer made in the last 50 years The vast majority have shifting problems that can be fixed with a simple cable adjustment. I don’t need to know anything about the derailer or drivetrain or miles or model of bike to properly assess and correct the problem…nor do you nor anyone else. They all work the same and any minor nuances are just that…minor. Once you realize that and that the cable is almost always the problem, fixing the problem become easy.

Feel good about figuring out the problem on your own. You did well and any thing I’ve said above is only minor quibbles that aren’t necessary but might make you life easier in the future.