Comparing Chain Wear Measuring Tools

I found this link to a pardo.net blog post discussing the limitations of chain wear measuring tools. I used to work in a bike shop and actually saw this happen with some 10 or 11 speed chains - we'd fit a brand new chain and the Park CC-2 chain checker would say "50% worn". So that post resonated with me.

summary Most chain tools measure the gap between a number of links and stretch the chain to do so. That means that any variation in the thickness of the rollers will be counted twice, so thinner rollers will make the chain "measure worn" prematurely. A proper tool will have three contacts with the chain - two to stretch it, then another to measure to the same side of the roller as the other measureing point.

The tool he suggests, the Shimano TL-CN41 (Pardo link, Shimano only seem to have a PDF of all their specialty tools) is only $60 or so delivered, so I thought I'd have a look. I already own a Park CC-3.2 (the "no moving parts" version) and a steel ruler, so I decided to do this comparison. Unfortunately I don't have a 10 speed chain to play with, and I'm not buying one just for this test.

I measured three chains, all 9 speed because that's what I use. One brand new (I opened the packet for the test!), the nearly-new one on my Rohloff-equipped commuter bike (well, ok, a couple of months at 200km a week so it's probably got 2000km on it) and the 1000km old one on my drop bar bike (9x2 derailleur gears).

Start with a new chain and the steel ruler. I've put one end in the vise and the other is streched out. The broad guideline is that 1/16" over the 12" mark a chain is worn out. Result: chain is not worn at all. Those divisions on the ruler are conveniently at 1/16" intervals.

Shimano tool says "not worn". And probably "bah!, cameras". It's got a very shiny sticker on it that makes it hard to photograph well. Park tool also says "not worn".

Commuter bike. The ruler says not worn. There's a couple of extra photos so you can see how I placed the ruler. Note that I moved the camera between the two close-up shots so the lens-chain angle is almost exactly the same in both cases to reduce parallax errors.

Again, the Shimano tool says it's fine. This time the Park tools says 50% worn but the ruler barely shows any wear at all.

With the drop bar bike the ruler possibly shows some wear, the Shimano tool shows some wear, but the Park tool says it's less than 50% worn.

Conclusion I don't think there's enough here to make a firm call. I'm going to take my camera to a friendly bike shop and see if I can try some more chains.