"No way would I run a 10-speed cassette and chain on a tandem; they even break on singles. This is bleeding-edge racing equipment."

I have never understood this thinking, hence my rant . Greg LeMond once said that he used Campi because it was indestructible. He could bend a rear derailleur back into approximate position and continue the race. Pro racers use Campi and beat the heck out of it. Race testing and outcomes eventually find its way into our daily lives, Campi included. Where do you think your anti-lock disc brakes came from? (Formula 1 and LMP racing).

I have used Campi for 35+ years on my single bike and never had a failure. (Granted, when they moved from friction shifting to index shifting, they didn't get it right the first time.) I am running Campi 10sp Record on both our tandem and on my single bike and have never had a problem. We also live and ride mostly in the hills.

My question is - how did your chain blow? Was it during the climb, under continuous pressure? Did you have a transition from flat/downhill to hill and mis-time the shift, and/or jump too many gears during the shift? Did you grab a lower gear during the climb and not back off your cadence (pressure) during shifting? If it was option 1, then it is probably a chain defect. Any of the other three options can blow a chain.