drosso66

Hi all,

I have somehow managed to pull the plastic barrel adjustment knob down and off of the metal adjustment ring that was underneath it on my Shimano Alivio Rear Derailleur.
I have tried and tried but cannot get it seated again.

This happened after I finally managed to adjust the H-Limit screw correctly enough to get the chain to go into 9th gear.
After I did that, I was then trying to do a restart/fresh start, following the instructions on a YouTube video from Park Tool.
That's when this happened. Totally my fault, not the video's. Also, the cable anchor has been completely loosened.
Right now, I am stuck once again. Any suggestions on fixing this would be most helpful and appreciated.

Thanks,

Dave R.

Crankycrank

Pull up the plastic knob and it will engage the adjuster screw so that you can turn it and it was designed that way. If you have the adjuster screw that far out probably best to re-clamp the cable at the anchor nut a little shorter.

drosso66

Thanks for your reply. I tried pulling up on the adjustment knob as I turned it---it's definitely hard to maintain a grip and turn it while pushing the knob up at the same time.

I can tell you that it wasn't this way before. The metal, notched ring underneath was not visible before---See the top of this pic:

Also, when I did pull up on the knob while turning it, as you instructed, the derailleur didn't move, in either direction.
Should I create some slack or take up slack on the cable at the anchor? Is there something else I can try?

Thanks again.

choddo

That looks pretty normal to me. It sticks out like that when it’s raised to tension the cable more by the turning of the adjuster. It is maybe a little high, turning it the other way (clockwise on the adjuster, no need to pull afaik) and then clamping the inner just a little tighter to make up for it might be worthwhile.

drosso66

Hi choddo,

I'm glad you replied to my new thread. (As for my other one, I spent a looong time getting the Zwift PC app installed (.NET Microsoft Framework fiasco)
and then another semi-eternity getting my Zwift Hub to pair up to my PC via bluetooth; when I finally got them paired, I had a hell of a time trying to find
the trainer difficulty slider to get it to zero, and then another looooonger time getting the chain to go into 9th gear. (Now it goes into 9th when I shift up to
8th gear, but at least I can make adjustments from the recommended 9th gear position.)

As for the barrel adjuster problem, at the moment, turning the barrel adjustment knob either way no longer moves the derailleur, I tried screwing it in all the
way until it stopped, and then backing it out, but it's just not budging.

Any ideas?

grumpus

You backed it out too far is all. As the cable is already loosened remove it from the derailleur, this will be easier with the cable out of the way. Refit the adjuster by pressing in the metal part while turning the plastic part clockwise - you only need to overcome the spring pressure until you get the screw started in its thread. Try it first without the spring so you can get a feel for how it lines up and where the thread starts, then repeat with the spring installed. You may find it easier to press the metal part with something (I just used a Philips screwdriver bit) that allows the assembly to rotate smoothly while you're pressing, and make sure the bike is positioned so you can easily reach and see what you're doing - there's no point making a fiddly job harder than it has to be.

drosso66

Thanks very much, grumpus. I loosened the cable anchor screw and got the knob adjuster to stay back up around the metal ring like it was before. I then tightened the barrel adjustment knob all the way down until it stopped.
At this point, am I supposed re-tighten the cable anchor screw before turning the barrel knob back? I only ask because right now, with the cable anchor loosened, turning the knob back does not move the derailleur, so I
just want to know if this is because the cable anchor wasn't tightened back up first, before I mess things up further.

drosso66

As I think about it, the cable obviously has to be secured tightly first, otherwise the derailleur is not going to move no matter how many turns I give the barrel adjuster.

grumpus

You already figured it out. 😀

drosso66

I tightened the cable anchor and started turning the barrel adjustment knob back until the derailleur began moving, and a few turns past that, and then tightened it to make sure the derailleur also moved the other way.
There seems to be a limited range, somewhere above and below the middle of the screw (?), wherein all movement takes place. Any loosening or tightening beyond these points no longer moves the derailleur.
Anyway, now I am ready to do the rear derailleur tuning from the Park Tool video I mentioned.
Thanks to Crankycrank, choddo, and grumpus for their great and kind assistance.
Cheers!
Dave R.

choddo

Correct. It’s a screw thread which is of a fixed length and once you go beyond that, the paired thread on the metal piece is no longer engaged and just sits on top watching it turn.

At the bottom end, I don’t know if there’s some kind of release to stop you damaging the thread once it’s gone as far as possible. But yeah, this range of fine movement should be plenty. The coarse adjustments are made first with the clamp position, within the constraints set by the limit screws.

soyabean

The adjustment screw should be clockwise all the way down when tightening that cable screw, and give it a little bit of pre-load tension too, that way the adjuster only need to make a turn or two at most.

When I install rear shift cables, I never need to turn our the adjustment after, nor need the high limiter screw. I usually get it right on the first attempt, and if not, I always get it on the 2nd.

grumpus

Sounds like the plastic part is slipping on the splines of the metal part - I'm not sure if this is a feature or a fault. But yeah, remove slack from the cable when tightening the pinch bolt and it only takes a turn or two to adjust the indexing, as long as the high limit was set right.

drosso66

Thanks for the new posts, choddo, soyabean, and grumpus.

When I clamped down the cable anchor screw yesterday, I didn't pull down on it to take up any slack as I tightened the screw. It sounds like I should have.

I am going to do that now, and then try to follow and perform the steps outlined in that Park Tool rear derailleur adjustment video.

drosso66

Fingers crossed, knock on wood, I just gained a much clearer understanding of proper alignment of the top derailleur cog with the sprocket of the current gear (9th).
With the bike being down low because it's mounted to the trainer, thus making it impossible to put up on a stand, it's necessary for me to get down on the floor and,
using a small flashlight for a clear view, make the the final adjustment accurately with the barrel adjuster.
When it looked to be in perfect alignment, I said a little prayer and got on the bike and started pedaling in 9th gear. No clicking noises, just the smooth chain sound.
Then I shifted down to 8th gear, and that was fine, too, Same with 7th. Then I shifted back up. The only possible issue was the shift from 7th to 8th---it seemed not to
engage at first and then did---a slight hesitation.
At this point, considering all the trial and error I've gone through, and not wanting to possibly knock something out of whack, I am inclined to stop fixing and finally
start riding. I couldn't have done it without the amazing assistance of the forum members here who replied with invaluable info. Thanks to all.
Cheers!
Dave R.

FBinNY 

This. The adjuster is simply too far out. Turn it all the way in and pull more cable down at the pinch bolt.

Tip- it's sometimes hard to get slack out. I shift to a mid to lower gear, then without turning the crank shift back to high. The chain holds the RD in, creating salck in the cable and I can get a good zero slack starting point.

grumpus

Hey that's my tip. 😁

FBinNY 

What a coincidence. We must be the only two.

grumpus

But there can be only one - choose your weapon.