An index adjustment on my (or my wife’s) rear derailleur used to be a cause for concern and consternation…and about an hour’s time to mess it up, then get it back into working order. Of course, that’s only if it didn’t take two (!): One to mess it up and realize it’s beyond my ability to fix, then another one to take it to the shop to have my mistakes corrected before I attempted to throw the bike like a frisbee.
Today, it’s a one minute adjustment (or a ten minute process if I’m replacing the cable altogether). In other words it’s not such a big deal. This post should make something that the cycling noob will fear, simple.
First, if your bike isn’t shifting quite right, we start with the barrel adjuster. When you shift, if it’s an “index” problem, you’ll notice that your bike is tough to shift either up or down the cassette (up refers to an easier gear, down to a harder one). Cables stretch amongst other things, so your bike will require some adjusting from time to time.
Now, without turning this into rocket science with bikes, you turn the barrel adjuster on the rear derailleur 1/8 to 1/4 turn in the direction that the derailleur is sticking. So, if your derailleur won’t shift up the cassette to an easier gear, turn the barrel adjuster counterclockwise – or in that direction… Then check to see how it worked by shifting through the gears. Still sticking? Try another 1/8 of a turn. Still? Try another 1/8 – if that doesn’t get it, you’ll have to go through an entire index adjustment. Conversely, if your bike won’t shift down, you turn the barrel adjuster in the direction it’s sticking, or clockwise. Just remember, turn the adjuster in the direction it won’t shift.
That’s as tough as it is, so don’t sweat it next time your bike is shifting a little rough. Pay attention to which way the chain won’t go, then give the barrel adjuster a turn in that direction. As long as there isn’t another problem causing the sluggish shifting (sweat corroded cable, cable sticking in the cable housing, etc), you’ll be right as rain.
For the full index adjustment, I’ve covered that once before. It’s really not very difficult.
One final thing to remember… Don’t mess with the set screws! Unless you’ve recently installed a new cassette (or crank/chain ring for the front derailleur) the chances that the set screws are off are somewhere between slim and none.