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I'm working on adjusting my front derailleur; Shimano 105 group set 5700 series. On reading on the net and also watching a couple of online youtube videos there is comments about the barrel adjustment used to either tighten or loosen the cable to ensure that indexing occurs.

Now what I'm confused with is that the notes often refer to increasing the wire tension via a counter-clockwise turn. The question is counter clockwise relative to facing which way ? For an inline barrel adjuster depending if i'm looking down from the shifter on the handle bars, or looking up from the cable end of the derailleur the direction is different.

Is there an easy way to know which way to turn ?

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  • A barrel adjuster is either screwed into the shifter or is composed of male and female pieces in the middle of the cable somewhere. When you "unscrew" to increase cable tension you turn the adjuster counter-clockwise (while holding the mating piece, if necessary), as viewed from the direction of the entering cable. If you think about it, "unscrewing" to increase cable tension makes sense, as it makes the cable housing longer relative to the actual cable inside. For an inline unit you can "unscrew" from either direction -- just do it from the cable's point of view in either case. Oct 31 '16 at 18:38
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As the mnemonic goes: "Lefty loosey - righty tighty"

The indicated way to turn is always relative to the object the screw / the thread is fixed to. Examples:

rear_derailleur

If you turn the barrel on th rear derailleur towards the wheel, it's loosening. It tightens away from the bike.

sti

The same goes for your STI: in this case loosening is towards the bar, tighening towards the front of your bike. If this was the STI on the right, it would be the other way round.

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  • It helps to know that the cable gets tighter when the shiny ring next to the grey knob (in the above picture) shows more.
    – Carel
    Nov 2 '16 at 8:29
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Everyone will tell you that the threads are right-hand threads. Hence you tighten the screw by turning clockwise. But turning left or right only makes sense relative to something else.

It's not too tricky if the barrel adjuster is at the shifter. It is tricky for an inline barrel adjuster, one in the middle of the cable.

It only made sense to me when I saw the hidden part that was meant as the reference object against which one turns clockwise or counter-clockwise.

To avoid confusion, it's easiest to unhook the cable from the derailleur's mount point and then disassemble the barrel adjuster all the way through. You'll get something like this:

(For a schematic and another explanation, see here under "Why? / Illustration").

disassembled barrel adjuster

The first surprise (perhaps) is that only one end of the textured barrel is threaded. The other side only "pushes". In other words, you'll find just one male and one female parts. You will not find two male parts symmetrically entering from the opposite ends of the barrel adjuster.

The second surprise is that the two metal parts (the two parts separated by a spring in the picture) depend on friction. You only need to grab the barrel and turn it; there is no need to grab the other half. You can often not even see or grab the other part anyway. What keeps the other part in place is friction with the cable housing. If some grease made its way between the top part (the male screw in the picture) and the cable housing, you could be turning the barrel while turning both parts. That acts as a safety mechanism anyway. There is no way to tighten with extra heavy hands (or even more forcefully with pliers) and strip the threads. You'd be simply "turning on empty".

Now, to introduce maximum slack in the cable, first wipe the cable housing attaching to the male screw from dirt. Then turn the barrel until you can no longer see the screw. It will disappear inside.

The next two steps are to attach the FD cable and then introduce tension as needed in the cable by turning until the part that was hidden starts protruding.

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  • When you put "that only one side is threaded" do you mean threaded, or textured for grip?the top piece has a male thread so the bottom piece has a female thread to match (i.e. they are both threaded). but yes on this style, only the bottom piece is textured/knurled and you grip and turn that one only. hence the tricky cleanliness/friction balance
    – Swifty
    May 2 '20 at 8:56
  • @Swifty Good point. I (think I) now removed the ambiguity.
    – Sam
    May 2 '20 at 9:02
  • oh I see, yes they are a bit surprising like that
    – Swifty
    May 2 '20 at 9:04

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