10-29-2013, 04:51 AM
I just use my hand and my eyeballs. It's actually not that critical in my experience (the chain was ridiculously loose when I got it and rode it for 700 miles, didn't really notice much of a difference when I tightened to within spec). Once you get used to what it's supposed to be, eyeballing it is quite easy, IMO. You just don't want it so tight that you snap the chain, nor so loose that it flies all over the place, hitting things. Kind of reminds me of the elaborate apparatus people use to align their rear tire (not that this is elaborate by any means, just that it seems unnecessary to me).