[Chris is me]

Originally Posted by asid61

I was actually asking how one would measure tension. Specifically, if the chain is ratcheting but it properly tensioned, does that mean that the shafts of the sprockets are bending, or just that the chain is stretching to the point where it becomes undertensioned, or something else? Or is "tensioned" for one team different from another?

Chain that is ratcheting is almost always not properly tensioned. If not, you either don't have enough wrap around the sprocket (a good rule of thumb is 120 degrees), or your sprocket / shaft is deflecting significantly. Both of these should be obvious. It's also possible that your sprockets are just way too small - a 16T #25 chain sprocket going to a 6" wheel is pushing it.

I still think that will have very, very little effect on whether chain details or not. 233 has done exact center to center for ages in a tube, but a tube that is far larger than the sprocket, so there is nothing constraining the chain top-bottom from coming off.

Chain is pretty tolerant to tension. You can dramatically over tension or under tension it with no issues as long as you maintain good lateral alignment and you aren't right on the upper edge of its load rating. Teams should be focusing on good lateral alignment no matter what style chain drive they run.

There's nothing mystical about running exact c-c chain...

Haven't used chain more than a handful of times in the last few years, but the last exact C-C run we did was very much properly aligned, but the span was so long that the chain stretched enough to start ratcheting. I agree with you that alignment is far more critical than tension and that chain in general is pretty forgiving, but I've just seen a few cases of failure in what looks on the surface like a good exact c-c chain setup. Maybe it's just crummy chain, or the runs are ambitiously long.

I've heard of teams that do c-c that just replace entire chain runs if the chain gets too loose. Other than cost and having to keep track of old vs new chain, I don't see much wrong with that approach.

While I've never done it, I've heard c-c for 35 chain is much easier. I imagine the chain's much greater load capacity reduces the effect of wear, not to mention the smaller number of links for the same length. But I really think 35 chain is overkill in most applications, you're just throwing weight away.