At the Mazama mountain pass ride we did two weeks ago was a couple who usually rides Tandem. But he was riding and she was not.
Turns out they crashed about 6 weeks ago. (dates not accurate here)
He had noticed little threads getting caught in his brake pads. Hm, that's odd.
well, they had a flat tire on the tandem and only 5 miles to go, so he pumped it up. Going downhill, the tire rolled OFF the tire. the moment the rim hit the road, the bike fell. She ended up with a broken hip and broken collarbone.
He walked. The poor guy is consumed with guilt.
Anyway; turns out the threads were the sidewalls UNRAVELING!
So yesterday i saw a piece of thread in my brake pad. Upon further examination, sure enough it was the sidewall. I am getting new tires tonight.