It does not span two bikes; I don't understand.
Yes I saw those "worn teeth" but they seem to be just a design feature.
The old chain is not flat top. Nor is the new one. The new one says XX1 on the box.
Interesting guide re chain stretch. I have measured it. On 1ft, the old chain is exactly 1/16" elongated. This is measuring it under tension.
The mystery is why the new (XX1) chain simply does not work at all. Maybe XX1 is no good for this bike? That link (no pun intended) points to a $180 chain and that would be a great way to find out it is a wrong chain
This is the old chain. SRAM EAGLE 352 and it has worked perfectly for a year, until it started sticking to the front gear at its bottom.
I have always kept stuff well oiled. Some say too well because it attracts dirt. So I tend to wipe the outside of the chain after lubing. I use the expensive Miuc-off lube, mostly the wet version.
I did a google on the 352 and it says it is just an internal SRAM code and "
If you are replacing your chain, any SRAM Eagle 12-speed chain (NX, GX, X01, XX1) will work with any 12-speed Eagle drivetrain." The 352 means nothing. So it says the XX1 chain should work but it totally does not.
But surely if the new XX1 chain needs a new rear cassette after 1 year, with the old chain worn to 1/16" elongation, that is ridiculous given how much they cost: £75 to £380 (for X01), and reviews suggest the cheaper end is trash. I checked for any correspondence and 1 year ago the front gear was £50 and the cassette was £170, which probably tells you what they are. Reviews of SRAM suggest the £170 parts are junk.
Just done a 1hr ride back on the old chain. It now skips on the smallest gear too! But I can adjust that out with the adjustment on the gear selector (on the handlebar). So I think this skipping must be somewhat related to the derailleur. I have a Q:
Obviously the upper derailleur wheel needs to be exactly aligned with the appropriate gear on the cartridge. But does the lower wheel have to also be aligned the same way? Mine is slightly off, as if the derailleur was slightly bent towards the wheel. But the bike has never had any impact. I would expect the lower derailleur wheel to be slightly "towards the middle of the cartridge" so the chain is somewhat guided to/from the front gear.