So, I have a ten speed 1979 Schwinn Continental II that I picked up for 25 dollars. The bike started fine with all the gears and components working, but the rear brake was squeeky. I replaced the rear brake, and when I put the wheel on I must have messed something up in the rear derailleur because then it wouldn't go into the lowest sprocket. I read about it a bit online and tried to mess with the rear derailleur. Now, I am stuck being unable to shift below the 3rd sprocket. I was wondering if anyone has any advice on how to fix it. Thanks!

Go to: www.parktool.com and find the instructions for adjusting derailleurs. Doing the steps in sequence is important.

If your derailleur is that far out of adjustment, I'd start by looking at the place where the cable attaches to the derailleur. If that's loose and has slipped some, it would cause exactly the problems you are seeing when you knock it around. If it's a really old bike, you might even be able to see a spot without rust/dirt/grime from where it used to be crimped, assuming this theory holds water. Good luck!

On my 70s era bike, a couple of times now all of sudden my rear derailleur stopped shifting down to lowest cogs for no apparent reason -- at least none related to cable tension. Both times it turned out the pivot point of my old derailleur had gotten gummed up so wouldn't allow the derailluer to release all the way outward even with cable entirely slack and limit screws set correctly. Take the wheel off the shoot a few drops of lube into the pivot points while you move the derailluer inward and outward with your hand see if that frees things up.