Yesterday I replaced the chainn on my 7 speed, 90's Schwinn hybrid-tourer using a SRAM quick link chain from the LBS, same as was on it. I took out two links to make it the same # of links. The old chain had over 1000 miles on it since December. I also cleaned the 14-34t Shimano magnarange free wheel till it was spotless, and took the cogs off the rear derailleur and cleaned and greased all the wheels. The bike has the Tourney group (I know, low grade) with a 7SIS Shimano derailleur. Everything worked good, I put a light code of dry lube on it and I spun around the neigborhood and through all the gears.

Early this morning I go out for a long ride, and dropped the chain while shifting to the big ring. In the process, the chain actually double loops as it drops off. It seemed like maybe it was too loose. It was still dark so I fought it for a little bit before giving up and calling my wife to come get me, as I was nine miles out of town.

Upon close inspection when I got home I found that one of the links was twisted, probably when the chain dropped.I The derailluers had been working fine, and I probably had 200 miles on the old chain since the derailleurs had been touched.

What is the best way to get the chain length right? One extra link with the chain on the big cog and big crank ring? Any ideas what caused this?