okay, i know that it fine tunes the tension on the shift cable. what i'm foggy about is which way to turn it if i have a shifting problem?

i can get good shifts 99% of the time, but there always seems to be at least one missed shift per ride. the cable is tight and i have the limit screws for the large cog\small cog set properly. i assume the barrel adjuster needs to be fine tuned, but i'm just kinda stabbing around in the dark with it. any advice?

Don't think of it as a tension adjustment. It's really a cable housing length adjustment.

UNscrew it (counter-clockwise) to "lengthen" the housing. This has the indirect effect of "shortening" the cable. This, in effect, is the same as gently pulling on an exposed portion of cable along the frame.

For my rear derailer, I can twist the barrel adjuster until I see the pulleys line up directly under the gear I intend the bike to be in. So, if I want the bike in the 3rd smallest gear, I turn the barrel adjuster whichever way it takes until I have eyeballed the pulleys directly under that gear. Generally, when it works for one gear, it works for them all. I think for my derailer, turning the adjuster to the left moves the pulleys toward the frame, but I could be wrong. Anwyay, it is very nice visual feedback on what happens when I turn the knob.

edit: this is a barrel adjuster on the derailer, not the one on the shifter which I do find somewhat baffling...

oh yeah, i should mention i'm talking about the derailer as well. i haven't really screwed around with the shifter at all.

thanks for tips. perhaps i just wasn't turning it enough to notice the alignment change when i was eyeballing it.

My device for remembering how to do this is to turn the top of the barrel adjuster in the direction that is shifting "slow".

So if it's rattling/delayed when going from small cogs to larger ones, turn counterclockwise (increase cable tension).

Also I usually shift into the smallest cog (least tension on the cable), make the adjustment, then go back to the "troublesome" cogs and test again. 1/4 turn increments, don't do anything drastic.

For a standard derailer(non rapid rise)

Loosen the cable so there is plenty of slack when it is on your top gear (7th). Adjust your stop screw so that the derailer is in line with that bottom gear. Now pull the cable tight, and tighten it. Now start pedaling the bike and shift it into 6th, if it does not shift all the way, back the barrel adjuster out so that the cable tightens and it shifts into the next gear, than click it to 5th and do the same procedure up to first gear. Then shift all the way back down to 7, it should shift fine all the way dowen without adjustments, if it doesn't there is a good chance you might need to replace your chain. If it stretch's then the bike will not shift correctly no matter how you adjust it.

Which way you turn the barrel adjuster depends on the specific problem you're having with your cable tension. Almost all rear derailleurs are "high normal," meaning the spring action of the derailluer wants to pull the derailleur outward, to the smaller cogs (higher gears, hence the term "high normal"). Front derailleurs are opposite of this, the spring action pulls the derailleur inward, to the smaller ring(s), lower gears (front derailluers are "low normal"). So to determine if the cable on, say, the rear derailleur needs to be tightened or loosened, you have to determine if the derailluer is out of adjustment in such a way that it's trying to pull a little too hard outward or inward. If you're in, say, the third cog, and you're hearing a little clicking back there and you determine that the derailluer is pulling the chain a little to the inside as it rides on this cog (trying to pull the chain to a larger cog, lower gear), then you've got too much cable tension and the barrel adjuster needs to be turned clockwise, which will, affectively, loosen the cable tension. If the rear derailleur is doing the opposite of this, trying to pull the chain outward, to a smaller cog (higher gear), then you don't have enough cable tension to counteract the derailleur's spring, and the barrel adjuster should be turned counterclockwise, to affectively tighten the cable tension. Front derailleur adjustments with the barrel adjuster work oppositely, because they're "low normal," but the principles are the same, and the cable is still affectively tightened by turning the barrel adjuster counterclockwise, loosened by turning clockwise. Good luck-

First, make sure there is no slack in the cable at the derailer when it is on the smallest cog. Then remember; trouble shifting to larger cogs, turn it counter clockwise. If the trouble is when shifting to smaller cogs, turn it clockwise. When you are close, small changes (1/16 turn) are in order to final it out. I find it easier to do this final tuning while riding, using the adjuster on the shifter. bk

The barrel adjuster does allow you to microadjust the tension on the cable. However it does not act directly on the cable. The barrel adjuster effectively shortens and lengthens the cable housing between its two fixed points. By changing the cable housing length you are changing the distance the cable runs and the tension on the cable. That tension is translated into repositioning the derailleur. The shifter and brake barrel adjusters work the same. All adjuster I have seen will work against the housing and not the cable.

Correct me if I am wrong.

Whoa, HardyWeinberg - GOOD IDEA! I never thought of that (DOH!), but it makes perfect sense. Thanks for sharing!

The best explanation of them all ;-)

lots of good advice here. thanks a lot guys.

I don't know how I missed your reply Speedub. My reply was unnecessary.

Experiment. Turn it both ways (keeping in mind how much you've turned) and see how your drivetrain reacts. You'll get the idea....

I happened on this thread while looking for information about how barrel adjusters work.

While the shifter side makes sense, I don't understand how the inner cable is kept in place with the ferrule:


What keeps the inner cable from sliding within the housing?

I only found this diagram, but it has parts I don't have on my bike.

Thank you.

Nothing keeps the cable from moving inside the housing...it HAS to move, or no adjustment would happen. The length of the cable never changes. When you turn an adjuster, any adjuster, doesn't matter where it is, it does the same thing..the length of the housing changes allowing you do make the adjustment.

Got it. The adjuster changes the length of the housing, which thanks for the springs, fine-tunes the pressure put on the derailleur.

If after you adj tension and are still having mis-shift issues you might find that the derailleur hanger may need alignment. Also barrel adjusters can twist or wind up the housing if the ferrule or housing end is jammed in the adjuster resulting in nearly impossible to fine to shifting. Pull back gently on the housing so the barrel turns independently of the housing.

Hey, great tip. I'll use that one on the punters, they'll love it.

"It's like the balance knob on a stereo..."