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Where does this piece belong?

Old 12-07-22, 09:44 AM
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pstock
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Where does this piece belong?

Found on my workbench.
has a raised nub on either side that looks like it would sit in a slot.
looks familiar but I cannot place it.

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Old 12-07-22, 09:57 AM
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Originally Posted by pstock
Found on my workbench.
has a raised nub on either side that looks like it would sit in a slot.
looks familiar but I cannot place it.
Cable adjuster detent.
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Old 12-07-22, 10:04 AM
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grumpus has it right. The plastic piece sits at the end of the spring that slips over the adjuster barrel. The piece's bumps than engage the der body's matching nibs to prevent unwanted rotation of the adjuster barrel. This is a Shimano item and found on their earlier SIS rear ders. Andy

And this part is off topic for the CR group
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Old 12-07-22, 10:14 AM
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from the rear derailleur

they don't always look the same














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Old 12-07-22, 11:12 AM
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Originally Posted by rumrunn6

You're looking at cable anchors the part in question is part of the barrel adjuster as seen as part of #5 here:

https://manualzz.com/doc/53870085/sh...-exploded-view
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Old 12-07-22, 02:33 PM
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Originally Posted by dedhed
You're looking at cable anchors the part in question is part of the barrel adjuster as seen as part of #5 here:

https://manualzz.com/doc/53870085/sh...-exploded-view
wow you guys are amazing. my bad, thank you
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Old 12-07-22, 04:39 PM
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Originally Posted by Andrew R Stewart
grumpus has it right. The plastic piece sits at the end of the spring that slips over the adjuster barrel. The piece's bumps than engage the der body's matching nibs to prevent unwanted rotation of the adjuster barrel.
For the same reason you cannot install a screw into a nut by merely pressing on it, the detects really don’t prevent unwanted rotation. They do feel kind of cool when you twist them, though.
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Old 12-07-22, 11:10 PM
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Originally Posted by smd4
......the detects really don’t prevent unwanted rotation.
Huh??
Of course they prevent rotation. The flatted oval shape keys to the barrel adjuster which is flatted to match. Then the nubs key to matching notches in the RD body.

The spring keeps it engaged to prevent turning, yet allows you to turn the screw when you want.
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Old 12-08-22, 09:53 AM
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Originally Posted by FBinNY
Huh??
Of course they prevent rotation.
No they don't. I used to have notches on the cable adjusters on my brakes. then I got new cable adjusters without them. The cable doesn't move on its own, because no amount of cable force will "push" the adjuster screw into the brake arm. Doesn't even look like Shimano installed them on the earliest Dura Ace RDs. I suppose it's possible, though highly unlikely, that vibration could cause the screw to move...

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Old 12-08-22, 10:00 AM
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My understanding of how barrel adjusters change their "setting" has nothing to do with vibration or the cable/housing pressure pressing on the adjuster/caliper. It's from the housing having a rotating nature as one moves the housing's other end about, as in the section of housing between handlebars and the frame. With each swing of the handle bars the housing twists a bit. If the frame stop adjusters were not able to stay put (lock nuts or the part this thread started with) the adjuster will turn within it's threading.

Perhaps the best proof of this is back when 5mm SIS housing was the standard and one used the shiny metal housing end caps the housing strands would sometimes produce a clicking/ticking sound as they scraped against the end cap's interior when turning the bars. Andy
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Old 12-08-22, 11:20 AM
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Originally Posted by smd4
No they don't. I used to have notches on the cable adjusters on my brakes. then I got new cable adjusters without them. The cable doesn't move on its own, because no amount of cable force will "push" the adjuster screw into the brake arm. Doesn't even look like Shimano installed them on the earliest Dura Ace RDs. I suppose it's possible, though highly unlikely, that vibration could cause the screw to move...
I responded to your statement rhat they don't prevent rotation. That's different than saying they're unnecessary. Had you said the latter I wouldn't have responded.

In any case, adjusters and similar applications do move over time and adding something to prevent that is SOP.
If we follow your logic, we'd never have problems with screws getting loose, and Locktite wouldn’t exist.

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Old 12-08-22, 01:55 PM
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Originally Posted by smd4
. Doesn't even look like Shimano installed them on the earliest Dura Ace RDs.
They weren't needed pre-SIS indexing as a small cable mis-adjustment had no effect on shifting performance.
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Old 12-08-22, 02:39 PM
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Originally Posted by dedhed
They weren't needed pre-SIS indexing as a small cable mis-adjustment had no effect on shifting performance.
I was incorrect when I typed "earliest." I meant the RD 7400--the earliest SIS derailleur.
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Old 12-08-22, 05:27 PM
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A bit of context might help.

First of all long spiral (index) housing changes the rules. The ends meet the adjuster at a small angle, and might bite into it a bit. Then with each shift a tiny pulse of higher tension imparts a tiny torque, that can walk the adjuster around in tiny steps.

Also keep in mind that the folks at Shimano had to justify the added cost of this design, and would not have spent the dough if they felt it unnecessary.

Lastly consider that index shifting was resisted early on as more trouble than it was worth. Today, nobody would blink at having to adjust trim from time to time, back then Shimano would have gone to lengths to avoid the issue.

So maybe not necessary, but logical at time.
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Old 12-08-22, 07:10 PM
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Originally Posted by rumrunn6
from the rear derailleur

they don't always look the same














those are not what the OP posted
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Old 12-08-22, 08:33 PM
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Originally Posted by FBinNY

First of all long spiral (index) housing changes the rules. The ends meet the adjuster at a small angle, and might bite into it a bit. Then with each shift a tiny pulse of higher tension imparts a tiny torque, that can walk the adjuster around in tiny steps.
I don’t know about you, but my index housing ends in a ferrule—which doesn’t move. The cable end doesn’t contact the adjuster directly.

Anyway, even what you describe won’t screw the adjuster deeper into the derailleur body. The physics just isn’t there.

Last edited by smd4; 12-08-22 at 08:39 PM.
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Old 12-08-22, 09:09 PM
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Originally Posted by smd4
I don’t know about you, but my index housing ends in a ferrule—which doesn’t move. The cable end doesn’t contact the adjuster directly.

Anyway, even what you describe won’t screw the adjuster deeper into the derailleur body. The physics just isn’t there.
So. I guess you're saying that Shimano wastes money because their engineers are a bunch of morons.

In any case, this thread, and my posts within it, isn't an about the necessity of these parts. It's simply an explanation of what they are, and what they (supposedly?) do.
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Old 12-09-22, 08:05 AM
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Originally Posted by FBinNY
So. I guess you're saying that Shimano wastes money because their engineers are a bunch of morons.
Wow! You guessed completely wrong! I've actually never seen such a wildly incorrect guess! Maybe instead of guessing my meaning, you could just work at comprehending what I wrote, eh? Or, failing that, ask for further clarification? Guessing is just a messy game.

The RD 7400 didn't come with an indented cable adjuster--and it seemed to work just fine (at least the one I had). My brakes don't use indented cable adjusters, and they work fine--no movement based on brake use. I get Andy's theory that the rear derailleur cable moves...slightly...and without a ferrule, the transverse cables in the housing could (theoretically) creep the adjuster barrel (although he seems to be referencing STI cable housing, and handlebar movement of the cables--I'm only referring to downtube shifters, with maybe a foot of cable housing in use). Even so, it's a theory I'm not quite willing to buy into.

The cable adjuster detents "feel cool" when adjusting cable length. They give a tactile indication of movement. They do nothing to keep the barrel adjuster from moving in or out. They are unnecessary. They are a neat little "value added" feature, like the detents on brake cable quick releases--also unnecessary. If you're going to "index" the shifting, why not index everything else?
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