And it's go! go! go!

In an effort to figure out this clicking of Mirabel's drivetrain I wondered, perchance, if it could be the chain?  Normally they wear pretty evenly but I supposed it might be some randomly worn section.  My Park Tools chain checker is a very precise and brutally honest go-no-go gauge: if it goes in fully* the chain is at least that worn.  And given that the tool is 'go' on the .75 side, and at some points on the chain it's 'go' on the 1.0 side, this chain is that worn.  I am quite surprised*, but on the other hand, I've already done nearly 1000 miles on the bike, and I don't know how many miles it did before I got it.

So even if a new chain doesn't solve the clicking problem – I hope it does, but it may not – Mirabel needs one pretty soon.

* It's also surprising how many people, some qualified bike mechanics included, don't know how to use this tool correctly!