While changing out a bad rear caliper* I was poking around waiting for my bleeding assistant and noticed some bulges in the undercoat on the frame just aft of the upper spring seat. Uh-oh. I started scraping and ended up with a perfect, business card-sized rectangle of rust. Fortunately, the steel is pretty thick back there, and I caught it in time. After cleaning it up I checked the other side. It looked fine through the undercoating, but poking around with a screwdriver revealed an identical rusty rectangle underneath! Something went wrong back here in production. Anyone else ever come across this? Sorry I didn't think to take pics before I treated it.

Best,
joe b in pdx

* a good reminder to check pad wear even after recent replacement. A stuck outer piston consumed an entire pad in about 15k miles! Mrs. joe b in pdx smartly noticed the sudden grinding noise, drove gingerly home, and saved the rotor.