Originally Posted by HerrKaLeun

No kidding. I had a CC-2 and it showed 0.25% on a brand new chain. Worst $27 I ever spent.

Well, it is really hard to see for me if the ruler has 0.5%. I tension the chain with the crank with one hand and hold the ruler to the middle of a pin. but every time I move my eyes from one to the other pin it seems to move a bit. lol. On both my bikes the ruler looked the same to me at an estimated 0.25%. But on one bike the CC-4-dropped in, but not on the other. so my measurement isn't necessarily consistent. Also note that the chain may elongate differently over it's length. So you want to take multiple measurements. That really gets old with a ruler.

Maybe the CC-4 is still a bit overcautious, but at least not like the other tools. And the 0.5% rule is not a scientific rule. If you have cheap cassettes, it may be beneficial to keep the chains longer. if the cassette is extremely expensive compared to the chain, you may want to replace sooner. My plan is to jsut measure monthly and replace the chain when the tool falls in and be happy with that.