Or maybe there just wasn’t enough pressure on the drops? Not sure…it was a standard 5mm QR w/ 9mm dropouts. Derailleur hanger is secured by two hex-drive flathead M4x12 bolts. One of them sheared off in the hanger.
As you may guess by the fact that it’s a QR gravel bike, the bike is quite old but I managed to find a derailleur hanger on line. Or maybe found one on line. We’ll see when it gets here. As a backup I’ve got a 2mm left-hand twist drill bit on the way. Either way some bike wrenching to occupy my time in the near future.
Anybody else shear off a derailleur hanger bolt? Or any trainer-induced breakage stories/advice?