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Shifter cable barrel adjuster(9 posts)

Shifter cable barrel adjusterdcv
Oct 12, 2002 7:51 AM
I ride a 2002 Jamis Ventura with Tiagara components. I'm having problems with the shifter cable barrel adjuster (on frame) for the front derailler. Everytime I shifter onto a smaller chainring, the adjuster rotates and loosens, decreasing cable tension. After riding 30 miles, the cable is so slack that I can't shift to a bigger chainring without re-adjusting cable tension. I've tried loc-tite on the barrel threads, no luck. Any suggestions would be greatly appreciated
stripped threads???C-40
Oct 12, 2002 8:13 AM
If you do a proper job of applying loctite, you wouldn't even be able to move the barrel adjuster with your fingers. Not a good idea.

Some bike frames don't even have barrel adjusters. You just shift to the smallest chainring and pull the cable as tight as possible before tightening the cable clamp bolt. A pair of pliers will help to grip the end of the cable.

You can defeat the barrel adjuster by tightening it down all the way before setting the cable tension.

Remember that the derailleur stop screws should be used to set the low and high limits of derailleur travel, not the cable tension. When a barrel adjuster is not available on the frame or the shifters, the cable will have too much slack if the low limit screw is backed out after the cable tension is set. A readjustment of the tension will be required. Not having a front derailleur barrel adjuster isn't ideal, but it's possible to live without.

The barrel adjuster may be loosening because you didn't tension the cable properly to start with. Screw the barrel adjuster all the way down, then pull the cable tight, with the derailleur shifted to the smallest chainring. You should not need to turn the barrel adjuster more than a fraction of a turn, and it may stay tight.
stripped threads???dcv
Oct 12, 2002 8:26 AM
I'm pretty sure the high and low limits are set correctly, and I used the weakest loc-tite available. I do think your suggestion for re-tensioning makes sense, the barrel threads are half in / half out (mid point of thread range) when cable tension is set for best shifting. I'll give it a try, thanks.
Are you sure....gogene
Oct 12, 2002 8:15 AM
.....the barrel is actually rotating? Are the threads in the frame where the barrel adjuster screws in, intact? Is it possible that your cable is not secure at the derailluer? Is it possible that the cable housing is cut a little short? It seems to me the last three things are more likely than a rotating barrel adjuster. It might even be worthwhile to put on a new cable and housing.
Are you sure....dcv
Oct 12, 2002 8:32 AM
The threads don't appear stripped, I'm able to tighten / loosen adjuster smoothly. I checked the nut holding the cable end on the derailler, was tight. Not clear on your question about cable housing cut short, how can you tell? How does that impact cable tension / adjustment? As for loosening / rotating, I confirmed the rotation by marking the adjuster w/ permanent marker, and actually see it rotating when downshifting (especially to granny ring). Thanks for the ideas, appreciate if you elaborate on the cable housing length (cable housing came as is from LBS ... bought the bike less than a month ago)
other things...C-40
Oct 12, 2002 9:04 AM
Be sure that the cable housings have metal ferrules at both ends and be sure that the ferrules are seated into the shifter and barrel adjuster before the cable tension is adjusted. If the cable ends aren't seated, the cable will lose it's tension as soon as the handlebars are rotated even slightly.
wrong about the length...C-40
Oct 12, 2002 9:01 AM
If the cable housing length is "too short" it would not seat on the the shifter and/or the barrel adjuster. In other words, you're suggesting that the cable housing could move independently after the cable was tensioned?

If you think about is carefully, you'll realize that cable could never be tensioned unless the cable housing contacts both derailleur and cable stop.

If the cable housing is truly too short, turning the handlebars far to the right will cause the front derailleur to shift to the big ring.
Like C-40 said....REPO42
Oct 13, 2002 4:59 AM
Ditch the barrel adjuster... tighten it all the way can also use vice-grips to hold the cable tight while you tighten the deraileur bolt...Now if you is slackens again after this then is it not the barrel adjuster screw... remember process of alimination(sp)
good luck
Update: Barrel Adjusterdcv
Oct 20, 2002 3:01 PM
FYI: I locked out the barrel adjuster (thanks C-40), that did the trick. I've ridden several times since then and the front derailleur / cable tension remains properly adjusted. Thanks for all the replies.