I thought it odd that people carry chain tools, but now I've seen the poor reliability of modern chains. Yuck!

I'll add spare master links (or quick links) to the list! On my recent century, we on the tandem ripped our chain apart twice, and thank goodness two people carried spares. They saved the day. I realize that tandems are hard on chains. Plus I was the strongest stoker photogravity had ever had, so I can claim it was my thunderous thighs that did it.