Originally Posted by
Iride01
To me, the article contradicts you on that statement. The park tool, CC-3.2, does in fact assess roller and pin wear to a certain extent. As well do others. Whether they are manufactured with consistent quality, I cannot say anything toward that. As simple as they are, there may be many users that simply misunderstand how to use them properly.
The problem is that we're dealing with a guideline or rule of thumb, not with any sort of precise measurement.
BITD the guideline was 1% stretch (1/8" over 12") based on pin to pin measurement. These days many choke down on that and use 1/2% (1/16" over 12"). Now people are talking about roller wear which was always there and factored into the pin to pin guidelines.
So tools that factor roller wear, especially short tools which may overly factor that, need to be compensated lest they read high. Unfortunately, they don't compensate for counting roller wear twice (once when the rule of thumb was developed over time, and again by including it in the actual measurement).
So, as mentioned, the gadgets are convenient ways to quickly check, but one needs to understand that they read high and reconfirm that "worn" chains are actually worn to whatever guideline one wants to use.
Think of these tools as you might a medical screening test, which is bias to generate false positive rather than false negatives (for good reason). When the screening test reads positive, you know you need to do the more accurate test to know for sure.