Quote:

the indices need to match exactly.




I think some have found the marks to be inaccurate. If you use any other accepted method (string, laser, pair-of-boards, etc) once, you can then either verify the marks to be accurate or do a one-time reference calibration/offset for future use.

By the way, my left chain adjuster routinely gets loose. It doesn't matter to me. After 37k miles and 3 sets of tires the bike tracks well and the tires wear just fine.