Please help me I'm so stressed over this. I just bought a new Supercycle bike from Canadian Tire. They did not adjust the derailleurs at the store so I decided to try it but I wound up loosen the cable too much and it came out of the derailleur all together. I am planning a cycling trip to Toronto on the weekend and I don't want to rent a BIXI bike for the entire weekend because that would cost a small fortune. Is there anyway I can fix this myself in a hurry? PLEASE HELP ME. - Andrew in Whitby, Ontario
Not to worry Andrew, help is available but it won't be easy. Derailleurs are basically the most complicated things to fix on a modern bicycle.
#1. First check to see if you have a bent derailleur tab. (You probably don't because your bike is brand new, but lets follow procedure here in case other people have problems.) If it is please see this other post on "Fixing a Bent Derailleur Tab".
#2. Get yourself a copy of Barnett's Manual (the books aren't cheap so a PDF will suffice) and read chapters 33 and 34.
I cannot possibly fully explain all the intricacies of fixing derailleurs in one blog post. Barnett takes TWO chapters to do it, one for front derailleurs and another for rear derailleurs. If you view the PDF it is pages 591 to 649.
Failing that check out this website: sheldonbrown.com/derailer-adjustment.html which is reasonably helpful, but has really shoddy graphics and skips over a lot of parts (It should be sufficient to help fix Andrew's problem however). That site does however get the point across that derailleurs are basically the most complicated things to fix on a modern bicycle.
Maybe someday I will do a detailed post on how to fix derailleurs, but if I am anything like Barnett such a post would take me a week to write and be 50+ pages long.
Good luck Andrew!