Originally Posted by
Shimagnolo
Unless your checker is the Shimano TL-CN41, pitch it and use a ruler to measure the chain.
The other checkers are primarily for *selling* chains, not measuring real wear.
Explanation here:
http://pardo.net/bike/pic/fail-004/000.html
As the link states, the other checkers are conservative, which is good enough for me (I use a Park CC-3, FWIW).
I'd rather error conservatively on replacing a relatively cheap chain, than get every last bit of use from a chain and perhaps end up replacing an expensive cassette or chainrings more often necessary.
YMMV.