What are the more common reasons for a chain throw-off ? What happened to me today was thus. Approaching lights. Slowed and stopped pedalling. At the same time geared down one level. Chain was on large ring. Did not gear down to the smaller ring. Chain popped off to the inside and wedged summat awful between BB and inner ring. This is only the second time in just over a year of riding this new ( carbon ) bike. Both times however have resulted in the same really tight wedging bewteen BB and inner ring and surface scraping to the BB area. Sure this not a good thing to happen with a carbon frame ! I believe derailleur set-up is good ( as I say, this certainly not a frequent occurence ). How do I virtually eliminate this event ? Is not continuing to pedal while down shifting the culprit here ?