CptjohnC

I bought a used bike sight unseen, as it seemed like too good a deal to pass up, and perhaps now I know why. I received it in the mail on Saturday, appearing to have been packed reasonably competently, and shipped in a bicycle box, apparently undamaged. Everything seemed fine as I began re-assembly, until I got to the point of putting on the rear wheel; the tension in the rear derailleur cage spring appears to be non-existent, such that the chain is completely slack unless I have it on the largest chainring and the lowest (largest) cog (and even then it is loose).

After checking Sheldon Brown and doing a search here, and futzing with every conceivable adjustment I could think of, I realized the problem is that the cage has no tension, so it isn't rotating back to keep the chain tight. This is a Shimano 105 Long Cage D, 2007 vintage, on a Specialized Roubaix.

While I have some cynicism about my fellow man, I am starting from the presumption, that since the bike was listed as being in great shape (and in the published photos, as well as out of the box it does appear to be -- except for my RD problem). The relatively logical conlusion, then, is that this must have happened in shipping -- perhaps the RD took a hard whack?

It appears that the cage is straight, but it also seems pretty far out of alignment, as it lines up with the second or third cog when it is shifted all the way to what should be the lowest cog, instead of lining up straight with the smallest. Obviously, this could just be a limit screw out of adjustment or something else, but I'm hesitant to mess with it, as the 'dead' spring makes it impossible to know what is really supposed to be going on.

The only post that I found here that appeared to be on point was the following post which sounds suspiciously like my situation (shipped bike, cage with no tension/ on the wrong side).

I'd love to resolve this situation if I can, but I don't want to make things worse or impair my ability to claim against the shipping insurance, if possible. I'll gladly supply pictures if you tell me what you want to see...

Thanks!

I_like_cereal

First thing is to remove the wheel and move the arm. If there is tension great. If its limper than a noodle replace the RD.

If there is tension or you are skipping step one. Reset everything to zero. Tighten the H and L screws and the B screw all the way down. Do the same with the barrel adjuster. Zero the rear D in using by slowing backing things out until you have it right.

Did it take a hit, was the box damaged? I find it hard to believe that the rear D took a hard enough whack that the spring lost its focus. I have taken some hard falls on the rear d and had to readjust my hanger, but the D was fine. Running a 105 long cage from probably the same year with plenty of miles on it.

Try to zero it out then readjust.

davidad

There is a return spring in the der. that can be serviced. If the lube has dried up you will need to take it apart and clean it.
https://www.parktool.com/blog/repair-...lleur-overhaul

pmt

Yes indeed, do that first.

CptjohnC

Thanks for the tips. I did a bit more study last night, and decided to try the procedure noted for a cage forcibly rotated past its stops. That seems to have done the trick, though I won't know for sure until I get a chance to take it for a shakedown ride this weekend. But with no load, it appears to be shifting smoothly, and such.

Now I just need to measure the chain stretch to see if I need to replace the drivetrain anyway... ;-)

billDennen

Curiosity reigns! What is "the procedure noted for a cage forcibly rotated past its stops" ??

CptjohnC

well, the right way was noted in the post I linked in my original post; it involved removing a bolt so that the pivot was loose, etc... I 'studied' the problem long enough to realize that with some gentle but steady pressure, the cage could pass its stop (which it did) without applying any sideways force to the cage itself (as I wanted to avoid bending it any more than it might already be).

It still looks straight, and it lines up nicely. Everything shifts well when not under load. Hopefully I will get a nice shakedown ride in on Saturday, at which time I'll either cheer for my success, or weep in defeat and go buy a new Derailleur (and chain, and cassette... I hope I don't need new chainrings....?)

zukahn1 

This is common on rear derailleurs the cage gets 180 degrees or 360 degrees out of position and it can often just be turned to the correct position so there is tension on the spring.

RoadieBen

I'm sorry for resurrecting an old thread but I had the very same problem today when trying to replace the cage at the bottom of my Ultegra 6870 derailleur. I had an epic nightmare for hours wondering why the cage would sit the wrong way round and the spring action was back to front ( it would spring towards the front of the bike causing the chain to be slack, rather than spring back to tension the chain). After removing and fitting the cage again and again for hours, I then Googled "derailleur 180 degrees out" and came across this thread on the first page of the results. So hopefully by posting this, I can help others who have the same problem.
So what was the solution?
zukhan1 vaguely touched.... At first I was fitting the cage to the derailleur as how I see it hang normally. So the cages spring was its natural resting position. This is wrong. After a lot of head scratching I noticed a big ridge thats moulded onto the body of the derailleur housing and a little protruding bar (looks like pin) that sticks out the side of the cage. What I was doing wrong was fitting the cage so this little bar was on the wrong side of this ridge before I was fastening the bolt! Then it clicked what to do....
1. slide the cage with its spring into the hole of the derailleur,
2. remember to get the ends of the spring located in the small retaining notches.
3.Then you need to wind the cage backwards so the little protruding bar is past this ridge, so it coils the spring under tension !!!!!
4. Then do up bolt.
This ridge and protruding bar is there to hold the cage under spring tension at all times.
As zukhan1 said, once you've slided the spring in the hole of the derailleur, you need to physically coil the spring backwards 180 degrees by pulling back on the cage until its bar or pin past the ridge, before you do up the bolt.

migrantwing

Try installing the spring in the 'higher tension' hole, too. I did that with my 5700 DR (nothing wrong with it, just an annual overhaul and thought I'd try the other spring position) and it now shifts snappier and more cleanly.