illdthedj

Hi guys!

to preface, i am not new to rear derailleur adjustment...i have many bikes and have built them all from the frame up, and have maintained them all with relative success.

HOWEVER im at a loss on a specific rear derailleur problem:

so its a dura ace 7401 rear derailleur.
using the limit screws, the derailleur is in perfect alignment with the low and high gears.
the cable is nice and taught on the 1st gear.
shifts fine from 1st to 2nd.

so when clicking up to the 3rd gear, its not shifting to the 3rd.
you would think "Oh ill just adjust cable tension till it shifts up!"

so i do that, and i can shift all the way up no problem.
then shifting back down...i get to the 3rd gear, click down to the 2nd.....and it wont shift....
"Hmmmm let out some cable tension?"

I do that, then i can shift no prob to 2nd gear.

but then i try going back up again, and sure enough 2nd wont shift up to 3rd....
more cable tension? but then reverse problem happens!

ARGHHH
it seems like theres no way to have it shift fine in both directions, only one or the other.


WHAT AM I DOING WRONG???
WHAT AM I MISSING?

please help me, and by doing so ill make sure to send you 100 internet karma points.

cny-bikeman

Inconsistent shifting, especially to larger cogs, when cable friction is not usually an issue, is often due to a twisted derailleur pulley assembly or hanger. Often the derailleur will work better (or differently) on the large chainwheel than on the small one. Have the hanger professionally aligned and have a good mechanic check to see if the derailleur is running parallel, or try a different derailleur.

dsbrantjr

+1 on cnybikeman's advice. Also, set the limit screws just loose enough to allow for crisp shifting and no looser; there is no need to visually align the pulley with the cogs; just tighten the screws too much and, while shifting by pulling and releasing the shift cable by hand, loosen them gradually until the shift occurs cleanly. Don't set the limits by using the shifter, you may confuse the effect of the shifter adjustment with that of the limit screws.

illdthedj

for some reason i had it always in my head that you visually align the high gear and derailleur using the limit screw, then shift up to the low gear and visually align that as well....
and this is how i've always done it, without incident (all my other bikes seem to be shifting nice and crisply setting them up this way)

HOWEVER this time around, i set them as you have advised (pulling and releasing the shift cable by hand)...

this has actually helped somewhat alleviate the problem...
IE now it does shift up and down from the 2nd and 3rd gears (and by this i mean the second and third highest...or smallest size gears) but not flawlessly...

so it will shift between the two....but its hesitant shifts.

FYI it shifts perfectly fine all other gears.

something tells me it might be a little bit of both of your advice? it is an older used derailleur....

cny-bikeman...
i understand it would probably take a good mechanic to have the derailleur "the hanger professionally aligned and have a good mechanic check to see if the derailleur is running parallel"....

however do you have any advice on how i can do this myself?

only because id like to learn how to do it myself....
or is that just not feasible...

anywho, regardless thank you both for your help so far!

cny-bikeman

I had shifting problem with my rear derailleur. I knew the hanger was likely bent - a result of poor handling of my bike (in spite of my precautions) on a return from Italy. I had over 20 years experience as a mechanic and did a lot of alignment work, but was unable to get it right until I took it into a shop and used their dropout alignment tool (don't count on a shop allowing you to do so). You don't say what number of cogs on your cassette, but I "only" have an 8 block and I needed a tool, so I recommend it not be done by eye if you want to make sure it's done right. So your choices in my view are to have a shop do it or to buy the tool yourself. Once you've done that it's not difficult at all to use - just need a properly dished/true rear wheel. Keep in mind it's not a tool that's needed often, but if you tend to work on other people's bikes it's worth the investment.

As for the derailleur - once the hanger is aligned put the drive train in high gear. Sight from in back of the derailleur toward the chainwheels. The pulley cage should be parallel to the chainwheels in both directions -not tilted in/out nor right/left. If you pull back on the derailleur to rotate the pulley cage it should remain parallel, not twisting to a different plane. Repeat with the drive train on a middle gear and small chainwheel. If it shows any indication of not aligning properly then replace it. The other option of course is to substitute a known good derailleur. If that one works and nothing you can do with the other one helps then replace it.

bradtx

illdthedj, There is no substitute for having a shop check something that requires a precision measuring tool.

Causes I've found for this most frustrating problem have been:
-a loose replaceable drop out
-a RD that must've been worn in a particular point of travel (tested with a RD from another bike)
-a too short cable housing to the RD

Brad

illdthedj

thanks guys...
without being in front of the rear derailleur right now, i will say i noticed some wiggle or play at the hanger pivot bolt....

i THINK the hanger itself is not bent, but thats just from eyeballing it.
the threads arn't stripped, and it isn't a loose replaceable hanger.



it definitely has play right at the pivot bolt where it attaches to the hanger...even when the bolt is tight, and the b-screw is properly above that little tab on the hanger.

im guessing its just a super used rear derailleur and just needs replacing
which sucks, because the bike in question is basically full dura ace 7400...and liked the idea of having a full matching groupset. im guessing buying another used dura ace 7400 rear derailluer poses the same sort of problem (IE pivot points being worn out)

cny-bikeman

Don't jump to the conclusion that the play is the problem, as it's not unusual to have some play at the pivot bolt - after all, it needs to pivot freely. Try the dropout alignment and checking the derailleur pulley cage first.

IthaDan 

What shifters are you using? 7400 was its own beast among its contemporaries. Even tricolor shifters won't get it to index right.

Other than that- cable friction. I believe there's an adjustment on the RD for the tension of the return spring. Crank that up for some friction forgiveness.

illdthedj

im using 740X brifters (i know they are 7400ish but not sure if 7402 or 7401 or what...

by "tension of the return spring"....im assuming you ARNT referring to the barrel adjuster for cable tension?

IthaDan 

No, on the underside of the RD, there's a little delrin cylinder with a slot for a flathead screwdriver. I believe there's an arrow on the little cylinder as well.

The slotted screw in this image left of center:

illdthedj

ill check that out, thanks!

cny-bikeman

Although I respect IthaDan's knowledge in general, his fix does not make logical sense to me. You described an initial problem with shifting inward to the 3rd cog - increasing spring tension will only make that worse. Increasing return spring tension helps when the derailleur is moving outward and it is dependent on the spring to pull the cable through the housing. One thing that is always adviseable, though is to make sure the shift cable is running smoothly, lubing with oil (not grease) if indicated.

Also I somehow missed asking, and nobody else did either - is the problem the same on both chainwheels?

miamijim

In general I've found these problems to be associated with worn out parts, primarily the upper g-pulley. Compensating for play will only allow the RD to shift well in 1 direction. Either or....

Go through the obvious first, is the STI lever properly flushed and lubed? A properly working STI lever will shift up and down without the need for cable tension. How hard do you need to pull on the cable to get it to shift back down into high gear? How's the cable friction? Disconnect it from the RD and apply cable tension by hand, it should minimal pulling... Form there check the upper 'G' pulley, it's designed to move left to right freely but it shouldn't 'rock'. Then there's the RD pivots themselves, grab onto the pulley cage and try to twist the RD body, there should be minimal looseness.

My money's on a sticky STI lever or a worn out RD....

cny-bikeman

Or you could just straighten the hanger and try a different derailleur. Checking all those things won't tell you what the problem is for sure, whereas eliminating the hanger and derailleur as variables will.

miamijim

That's one heck of a way to fix something....

Pay to have something straightened that may not be bent and replace a RD without knowing if the old ones bad. Everything mentioned in my post can be checked for free, at home.

cny-bikeman

The hanger recommendation was due to the fact that problems that occur only in certain combos are often traceable to a twisted hanger, which cannot always be easily detected by eye. At some point after one has checked the usual fixes the derailleur hanger needs to be eliminated as a possible cause or contributor, and the only way to do that is to have it checked.

I did not say to replace the derailleur, I said to try a different derailleur, as I mentioned earlier. It does not hurt to lube/flush the shifter, but there is nothing in the shifter mechanism that would cause a differential shift up the cassette. Likewise with cable lubrication, which I already mentioned as a good idea. Checking the derailleur pulley and pivots does not tell you if they are the problem - if you find they are loose the next step would be....try a different derailleur. As most people have not handled multiple brands and models of derailleurs they would not necessarily be able to tell if a certain amount of play is normal or not, so one cannot conclude from feeling play that the derailleur must be replaced.

Kimmo 

I've cured upper pivot slop on both Campy and Shimano derailers, by disassembling the pivot and inserting a washer. Had to mess around with the washer a bit, filing it thinner and maybe putting a notch in the side IIRC, but it worked a treat.

The pivot was a little stiff afterwards, but since it wasn't too stiff to respond it worked fine.

illdthedj

wow i appreciate all the comments. im going to have to go thru each one by one with the bike/ rear derailleur in front of me...ive been away all weekend but i will definitely try out all recommendations posted here.

my knowledge in regards to rear derailleurs is limited to knowing how to install them and adjust them...that is if the rear derailleur itself is in proper working condition, which obviously in this case it is not.

i know it isn't a problem with the shifter itself, at least it dosn't seem to be, since its shifting quickly and dosn't have any of that sort of "gummy" shifting feel i've felt with other older shifters.

my guess is though, that the play in the pivot is what is causing the problem....only because that is what is most obvious to me at the moment. this is actually my second 7400 rear derailluer (both purchased use) and the other one does not have this same sort of millimeter or two of play originating from the pivot bolt.

but i will be dedicating some time to this sometime this week, and ill check out all recommendations made here, including simply using a different rear derailleur for comparision (i have a tri-color knocking around in the parts bin)

thanks guys!

illdthedj

btw...here is the rear derailluer (and bike its attached to in question)


it is more or less fully 7400 dura ace, so im hoping to fix this derailluer instead of finding a replacement

miamijim

You need to turn out the 'b' screw.

Al1943

As I'm sure you know, the 7400 is the only RD compatible with your 7400 shifters. It has a unique actuation ratio.

bradtx

+1

The 600 won't be a proper comparison (with the DA shifter), only another 7400 will.

Brad

hir0

did you try pushing the derailleur by hand through all the gears without the cable? did you consider the cassette?

illdthedj

haha actually i did NOT know that...
i guess ive never been unlucky enough to find that out on my own...

ive only used the 7400 RD with the 7400 brifters.