Originally Posted by
easyupbug
Were we astronomers parallax would be important but as cyclists a 12" steel rule works well.
I use a 3' tape measure using the 1" & 37" marks to avoid an error from the "hook".
It's short enough to avoid "parallax" and you get 3X the resolution. A 4' section is too long for me to make sure a chain "end" doesn't shift.
OP, if you are using a chain checker, check the checker.
Mine reads .25% more wear than reality. As long as you know how much error your checker has, it's easy enough to subtract that for a quick, easy check without getting your hands greasy.