Shifting cable tension problem
04-17-16 | 05:34 AM
#1
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Shifting cable tension problem
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-
So, letīs start with an overview of the system:
- Microshift 9s Bar end shifters
- Jagwire road cables and housing, leaving the tape just before the bends of the (drop) handlebar, aka almost imediately
- Shimano Deore 9s Rear derailleur
It worked perfectly until I replaced the cables & housing some weeks ago. Ever since I cannot set it properly.
My general procedure was to screw the rear derailleur barrel adjuster almost all the way in, cable anchored loose and system in the least-tension setting, aka smallest sprocket. Start pedalling on the workstand, move the shifter to the next position (which at this point does not translate into an actual shift of gear) and start unscrewing the barrel until the derailleur finally takes the chain to the second smallest sprocket. Normally, once I achieved there were only some minor adjustment left and that was it.
Not this time. I achieve the shifting from smallest to second smallest but then troubles start to occur.
- Completely loose, the shifter moves along its whole arch (it makes 8 clicks). When tensioned as above it only makes 7. In position 8 it is as if there is too much tension for it to get to position 9.
- Also, and related, at some point, the shifter shifts two gears, if I recall correctly, it jumps straight from 4th to 6th. If I loosen the cable (screw the barrel) enough to have tha chain go back to the 5th then I have problems with the 1st and 2nd sprocket.
- One last clue worth mentioning. Right now I have "auto-shifting" Sometimes when I press the pedals too hard after stopping the system shows a high-normal tendency to shift some gears higher, And it is not just the derailleur, the bar end itself auto shifts.
Long story short I either have too much or too little tension and I somehow cannot reach the needed middle ground.
Letīs now get to the real question I wanted to ask. I once heard - but could not find much info about it - that tensioning the cable should be achieved by working on both the derailleur barrel adjuster and the down tube (or shifter) ones. I always relied only on the mech one. considering the DT barrels to be there for on the fly adjustments only. Could this be at least part of the problem. If so, how should I work on the system as a whole?
04-17-16 | 05:54 AM
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Have you checked your derailleur hanger alignment? It doesn't have to be off very much to make 9-speed and above drive trains act the way that you reported. Even if that's not the problem it would be good to make sure that's not an issue before driving yourself crazy with repeated tension adjustments.
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04-17-16 | 09:27 AM
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Letīs now get to the real question I wanted to ask. I once heard - but could not find much info about it - that tensioning the cable should be achieved by working on both the derailleur barrel adjuster and the down tube (or shifter) ones. I always relied only on the mech one. considering the DT barrels to be there for on the fly adjustments only. Could this be at least part of the problem. If so, how should I work on the system as a whole?
It makes no difference whether you do it with an adjuster on the shifter end or the derailleur end, or by moving the cable in the clamp bolt, the effect upon shifting is the same.
04-17-16 | 02:13 PM
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Are the casings fully seated and end capped correctly. If the casing isn't tightly up against the hard stop (frame stop or lever seat) it can move during the shifting. And of course there's the cable anchoring that's routed on the wrong side of the bolt or tab. Andy
Last edited by Andrew R Stewart; 04-17-16 at 02:14 PM. Reason: added idea
04-22-16 | 06:54 AM
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Are the casings fully seated and end capped correctly. If the casing isn't tightly up against the hard stop (frame stop or lever seat) it can move during the shifting. And of course there's the cable anchoring that's routed on the wrong side of the bolt or tab. Andy
The way the cable is anchored should also be ok, as I checked the instructions right before doing it to be sure.
Still, the first time I take the bike back on the workstand I will make sure to check for everything all of you suggested.
04-23-16 | 05:33 AM
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In the future, I suggest starting with the question then following with the details. With the details first, no one knows their relevance or significance is until they get to the question. With the question first, the readers have a shot of understanding how each detail might relate or contribute to the issue it as they read them.
04-23-16 | 07:10 AM
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First, it is not logical to ignore the fact that the OP did not have a problem until changing out cables/housing. Secondly, a bent hanger rarely causes the described problem when on the same chainring. The most likely cause is friction in the cable/housing system - from incorrect cutting, caps, kinked cable or wrong housing length.
