Originally Posted by
Racing Dan
From my experience rollers wear faster much than true elongation. For that reason Im not hesitating letting the "between rollers" measurement grow by as much as 1mm between 12 rollers, from ~132,25 -> 133,3mm, as explained in an earlier post. That is more like 0.8%, but at that point true elongation is still less than 0.5%. Beyond that point the chain may technically not have reached 0.5% elongation, but imo shifting and "smoothness" is impacted and id rather just replace it regardless.
Again, no one knows what the old Park, and other gauges that measures between rollers, considers "+0.5%" or "+0.75%" but if they are anything like the campy recommendation, 132.6mm, you be replacing chains way too soon. - Some one needs to measure the gauges before we can judge if they give a reliable indication if the chain is ok or worn out, or they just make you bin your chain way early to play it safe or not enough thought went into the design. Heck, no one even knows if "+0.5%" is the same thing on different gauges.
Also who made "+0.5%" the gold standard for 11s drive trains and for what reason. +1.0% used to be the engineering standard for any chain.
For the above reasons I went with a digital calliper and made up my own rules based on experience. Subject to be revised along the way.
With the wear self-accelerating I think that the primary purpose of checking the wear and replacing chain is to avoid getting into a runaway situation. I.e., the extra time/distance that you get to ride from 0.5% to 0.7% is well shorter than from 0.1% to 0.3%. The common expectation is that once you get to 1% is that you likely need to change the cassette even if it is on its first chain. To test the above one would need to map chain elongation against covered distance from the time when the new chain was put on.
Indeed the various 0.5% or other markings could mean anything, including accounting for the estimated roller wear. I went to measure the increase in threshold distance for the simple Park CC-3. Between the 0.75% and 1% markings the distance increases by 0.21% rather than the expected 0.25% or higher if they were accounting for the stronger roller wear.
I never paid much attention to roller wear as isolated from pin-to-pin stretch and may look into that from now on. I even have a relatively new chain on the main bike and I usually have another identical chain in storage that I could use in comparison. I also have various measuring instruments and could measure virtually whatever I would want. However, the issue is of how much time to dedicate to that. The chain is central to the bicycle, which makes it an interesting problem, but there are so many other problems in the world. I skip chain cleaning because it is time consuming bother - it also elevates chain replacing for me somewhat.