When my dealer changed my tires back in July, they left about four inches of slack on the chain; way too much. The spec is 1.0 -- 1.4 inches. I could hear it slapping all the way home. So when I got home, I pulled out my 27 mm socket, loosened the axle nut and took the excess slack out.
Realignment of the rear tire follows the typical method of aligning the slides (both sides) against the notches on the swing arm. Seems fairly simple, but it seemed like every time I looked at it one side or the other didn't appear properly lined up with the other.
The problem is two-fold. The first, and biggest problem, is my visual acuity isn't anywhere close to where it used to be. Even with reading glasses, it's hard to focus in on real small things. The second, is that the alignment notch on the slide block is recessed in the swingarm while the row of alignment notches on the swingarm are on the outer edge. So the lines don't come exactly together anyplace and it's like a 10 mm spread. It makes for somewhat of an optical illusion trying to align the slide notch to the right place inside the sidearm notches that are about 4 mm apart in and of themselves.
I put up with worrying about it long enough and, in connection with some major services I have going on, I decided to get it right on. Very simply, I located a rigid plastic drawer divider that I held to the back, flat surface of the swingarm. Any thin, thin rigid material will do.
Then I measured the front of the slide to the plastic piece with my caliper. Repeat on the other side. What did I find?
The measurement was exactly 66 mm on each side. Exactly! Hey, maybe my old eyes aren't so bad after all. :)
Two good things come out of this. First, I won't be worrying if my tires is out of alignment because I can't see well and, second, I have a new method to measure alignment going forward. Sweet!