Both were pretty sudden actually. I don't remember the Schwinn making a noise when it broke, but I was commuting home and suddenly the bike felt "wobbly." Granted it was 5+ years ago so maybe it did. I can't really see any rust because now it's welded over and grey. It looks fine elsewhere besides some paint wear.

The aluminum definitely made a noise and was sudden, but the derailleur slamming to the small sprocket when the shifter cable snapped (due to the chainstay snapping) was probably part of it. There is no rust or anything on this bike. Just a clean break through the weld area.

My knees would prefer a higher cadence style as well I'm sure. It just feels so uncomfortable.