Mary heard a faint sound from the back of her bike that neither she nor I could track down. Standing in the garage, we decided it was slightly louder when the wheel turned backwards, but the sound didn’t correlate with anything.
Eventually, I held my hand over the wheel while turning it, whereupon the problem made itself obvious:
Another Michelin Hair from a steel-belted automobile or truck tire!
The short hook on the right side embedded itself the in the tread, with the rest sticking out. Turning the wheel backwards dragged the longer arc on the fender, making a slightly louder sound. Of course, the tightest fender-to-tire clearance occurs just behind the seat, where it isn’t easily visible.
Fortunately, the hook wasn’t quite long enough to punch through the Schwalbe Marathon’s armor layer and the tire liner.