Originally Posted by cyccommute

The outer plates on a discarded chain can be moved relative to each other but I will admit that it took more force than I expected. This chain was a worn out chain >0.75% elongation but not a highly worn chain. I have handled highly worn chains where the outer plates are easier to move.

The pin shows little noticeable wear.

I will admit that I was mostly incorrect about the fit of the outer plates. However, this whole “outer plate force fit” argument is a red herring. The fact that the plates fit tightly on the pin does not mean that that is the cause nor even a contributing factor to the plate fracturing. A chain plate fracture is something of a rare event. I’ll remind you of what was said

If the force fit put that much stress on the plate at every pin, fracturing of pin plates would be a much more common experience. It happens, yes, but it doesn’t happen all that often nor do people put chains in highly acidic cleaners that have an affinity for iron and then notice that the chain makes a popping noise when they do so.

I have said over and over and over in this post not to use naval jelly on chains and that I also wouldn’t suggest any kind of cleaner for a very rusty chain. Chains aren’t worth that level of effort.