Gattonero wrote:if anything, the Park Tool CC1 has to be the least tool to use: apart from taking a measurement of only 7 pins (IIRC) vs the 11 pins used by the CC2.2, the reading dial moves on a bolt that is bound to have a noticeable play, which in turn can give a more pronounced error of the effective wear.
I have compared hundreds of times the CC1 with the CC2.2 and many times a chain that would be in the "safe zone" with the former, turned out to be already in the 0.5% wear mark of the latter, hence not safe to be replaced alone in most cases.
I agree, a short measuring tool is bad and I'd also suspect moving parts of introducing further error, but given that it's measuring inside
the links, those errors should all trend towards over-reading, failing good chains rather than passing bad ones, so I'm puzzled that your better tool fails chains that the bad one passes. I guess the CC1 is just completely up the creek! But whatever, Park don't make that tool anymore. They seem to have replaced it with the CC2, which is longer (which is better) but still has a moving dial, although differently arranged so perhaps less wobble-prone.
As for CC2.2, I'm afraid I can't find it anywhere. Do you mean CC3.2? I've got the old version of that gauge, the CC3, and that measures 10 links/pins, so maybe that's what you've got too. Its replacement (CC3.2) measures 14 links/pins: even better!
None of these exactly correspond with your odd numbers of pins however. Are you sure you've got that right? Remember that the end of the tool engaging an inner link merely presses the roller onto its bush and does not have any effect on the corresponding pin/bush joint, so that one doesn't count. All of the tools I've checked in the flesh and on the interweb measure an EVEN number of links and instances of pin wear. As pointed out by Jobst Brandt in his interesting page on this subject
, since pin wear affects only the outer links (across an inner link the rollers may get sloppy, but stay the same distance apart when pushed in the same direction), for consistent results in chain measurement this must
be over an even number of links.
And here's a thing: I've been making some measurements of bits of chain (in response to someone else's suggestion that roller slop is somehow equivalent to pin wear - it isn't) and found that whilst dismantled inner chain links, pin-hole to pin-hole, are as exactly as I can measure, half an inch (12.7mm) long, outer links are slightly shorter than that: by an amount equal to the difference in diameter between the pins and those holes. The difference was 0.05mm in this case, which means each pin can shift 0.025mm off-centre, so two inner links can pull apart by 0.05mm across the outer link that joins them, which measures 12.65mm across pin centres. Thus the new chain is just right when you pull on it. Neat eh? I also found that the rollers, even on this brand new chain of good quality (Shimano HG73) were almost ten times more sloppy than the pins: being able to shift to and fro on their bushes by an average of 0.4mm total movement (i.e. can shift off-centre by 0.2mm)!
Two questions I was tying to answer with my measurements is how much difference roller slop actually makes to the use of a chain gauge, and do Park Tool make any allowance for it when they design such a gauge. As already noted, the Park CC3 measures 10 links which should measure exactly 127mm, pin centre to pin centre. But the gauge fits between rollers so subtract one roller diameter (7.67mm) = 119.33mm. The 1% side of the Park Tool measures 120.6mm, which is 1.27mm longer than that, which very neatly is 1% of 127mm. QED! However: when you fit this chain into the tool it will push those rollers apart some 0.4mm, which is 0.3% of 127, so the chain will fail this side of the tool when only 0.7% elongated. And that's assuming the rollers don't get any more sloppy than when the chain was new.
So the answers are that roller slop makes a substantial difference to the measurement, that Park Tool doesn't allow for at all.