# Dura Ace 7800 rear derailleur won't drop to smallest cog



## OldZaskar (Jul 1, 2009)

Shifts crisply and quickly through the other 9 cogs. But will not drop into the smallest cog... well, 1 out of 4 times it will after about 10 pedal rotations and a lot of chatter. Or, if I manually "nudge" the derailleur, it'll drop down. Here's what I've tried to rectify the issue...
1. Adjusted limit screw - actually dialed it out so far, I took the screw out. 
2. Replaced the cable and housing
3. Made sure the loop is not too tight - it's actually, bigger than the other bikes I compared it to
4. Double (quadruple) checked the orientation of the lock nut retainer - the backside nut/clip
5. Cleaned the drivetrain
6. Inspected the chain - length, kinks, etc. 
7. Inspected the derailleur - moves smoothly, no bends, etc.
8. Inspected hanger - straight and tight 
9. Removed cassette; made sure correct spacer is there - not missing, doubled, etc. 

I had a friend over to make sure I wasn't missing something simple - he's a better mechanic than me - and he repeated everything I did... with the same results. Is it possible the derailleur just worn out? I have to be missing something. Thoughts?


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## MR_GRUMPY (Aug 21, 2002)

Is the cable too tight?

Is there sports drink residue in the cable guides under the bottom bracket?

Is there sports drink residue in the rear derailleur??
.
.


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## cxwrench (Nov 9, 2004)

OldZaskar said:


> Shifts crisply and quickly through the other 9 cogs. But will not drop into the smallest cog... well, 1 out of 4 times it will after about 10 pedal rotations and a lot of chatter. Or, if I manually "nudge" the derailleur, it'll drop down. Here's what I've tried to rectify the issue...
> 1. Adjusted limit screw - actually dialed it out so far, I took the screw out.
> 2. Replaced the cable and housing
> 3. Made sure the loop is not too tight - it's actually, bigger than the other bikes I compared it to
> ...


by this do you mean the 'cable fixing bolt & plate'? you know what i'm talking about, yeah?


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## OldZaskar (Jul 1, 2009)

The bike was cleaned pretty well before the repair. Surely the sports drink wouldn't hold up that. ;-)



cxwrench said:


> by this do you mean the 'cable fixing bolt & plate'? you know what i'm talking about, yeah?


 Yes - that's the term I was looking for. I probably checked that 10 x. 

UPDATE:

Swapped the 7800 derailleur with another 7800 derailleur that was working perfectly on the other bike, with... uhm - different results. The bike will now shift into the smallest cog BUT requires two shifts to get it to move up to #2. From there, it's smooth up to #7... then it chatters a ton as it fails to move to #8. A couple turns of the barrel and it moves up nicely through #10. But, then it requires two shifts to go back down. 

This is where I feel like I've got OCD - must check cable fixing bolt & plate... again, and again. Because it is really behaving like that's the issue. Three of us looked at it... again and again. 

Two of us took turns trying to tune the derailleur - starting in big ring, smallest cog... one click - chatter, chatter - slowly add tension 'till chain moves to #2. Chain would move smoothly up to #7 then same results. We'd start in the small ring and work backwards - same result. The odd thing was how the shifter required 2 shifts to "change direction", e.g. it would shift up, up, up, up, fine - with one click. Or, down, down, down, etc. With one click. But any time - anywhere on the cassette - I went up, up, up, down, that would require an extra shift, e.g. down, down. do dump one cog. Very odd... at least for me - first time I've experienced this.

At 10:30 pm last night, we threw in the towel. "You have two options. 1. Take in. 2. Buy shifters." We came to the conclusion that the shifter is worn out. Because when you exhaust your wrenching abilities, you solve it with expert help or new parts.


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## steelbikerider (Feb 7, 2005)

Is the shift lever set properly before the cable is installed - all clicks done so it will start at the small cog? 
I've done that before.


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## OldZaskar (Jul 1, 2009)

steelbikerider said:


> Is the shift lever set properly before the cable is installed - all clicks done so it will start at the small cog?
> I've done that before.


Great question - I should've added "We dumped the shifter to make sure we're starting at no.1"


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## Kontact (Apr 1, 2011)

How about paying a bike shop $10 to fix it before buying new $400 shifters?


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## wblas3271 (May 12, 2012)

Either a bent hanger or too much cable tension.


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## wim (Feb 28, 2005)

OldZaskar said:


> This is where I feel like I've got OCD - must check cable fixing bolt & plate... again, and again. Because it is really behaving like that's the issue. Three of us looked at it... again and again


What are you checking the fixing bolt clamp position against? The drawing in the Shimano instructions? I ask because the drawing shows the derailleur as seen from below (or with the bike turned upside-down) and from the non-drive side of the bike. This is an unusual view, so it's not that hard to get it wrong.


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## OldZaskar (Jul 1, 2009)

Kontact said:


> How about paying a bike shop $10 to fix it before buying new $400 shifters?


Did you miss this part?:

"You have two options. 1. Take in. 2. Buy shifters."


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## OldZaskar (Jul 1, 2009)

wblas3271 said:


> Either a bent hanger or too much cable tension.


The hangar was just replaced - on a carbon frame. I'm assuming that rules out frame/hangar bend... hard to bend carbon. But, to your point, we did suspect a bent derailleur cage... until we swapped it. 

When we cut the cable, the derailleur did not drop do the smallest cog. Which had us re-re-re-recheck the high set screw... again. 

It is time for the doctor and marketing guy to bow to the shop mechanic... we're stumped.


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## Kontact (Apr 1, 2011)

OldZaskar said:


> Did you miss this part?:
> 
> "You have two options. 1. Take in. 2. Buy shifters."


No, I didn't miss it, I was referring to it. They aren't exactly equivalent options. Of course you'd take it in, first. When would buying shifters ever be the appropriate choice in this case?


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## Kontact (Apr 1, 2011)

OldZaskar said:


> The hangar was just replaced - on a carbon frame. I'm assuming that rules out frame/hangar bend... hard to bend carbon. But, to your point, we did suspect a bent derailleur cage... until we swapped it.
> 
> When we cut the cable, the derailleur did not drop do the smallest cog. Which had us re-re-re-recheck the high set screw... again.
> 
> It is time for the doctor and marketing guy to bow to the shop mechanic... we're stumped.


If the hanger was replaced, it probably _isn't_ straight. Replaceable hangers are not precise and are made of soft aluminum. They must be checked with a hanger gauge after installation, and should be checked anytime you get suspicious shifting because they bend easily. You absolutely cannot see the amount of bend that will cause shifting problems, and they have to be square horizontally and vertically.


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## OldZaskar (Jul 1, 2009)

Kontact said:


> If the hanger was replaced, it probably _isn't_ straight. Replaceable hangers are not precise and are made of soft aluminum. They must be checked with a hanger gauge after installation, and should be checked anytime you get suspicious shifting because they bend easily. You absolutely cannot see the amount of bend that will cause shifting problems, and they have to be square horizontally and vertically.


Good call. Not having such as gauge... and not knowing how to use one, I think this solidifies the decision to run it over to the shop. And, we'll mention to the mechanic that we suspect a misaligned hanger...

Thanks!


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## Al1943 (Jun 23, 2003)

I would shoot the shifter full of WD40 to soften hardened grease and clean out dirt and crude that may have accumulated.


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## Kontact (Apr 1, 2011)

Al1943 said:


> I would shoot the shifter full of WD40 to soften hardened grease and clean out dirt and crude that may have accumulated.


Considering that WD40 dries leaving a waxy film, I'd use something else. Spray Triflow works well for STI.

I don't think blasting out the factory lube is a good idea until the problem is actually shown to be an internal shifter problem.


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## erik1245 (Jan 6, 2012)

Are all the spacers/nuts/washers on the axle where they're supposed to be? As in, nothing extra on the drive-side of the axle?


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## Jeffry (Jun 15, 2012)

Have you also replaced the derailleur wheels? I had the same problem. The upper wheel could have been worn out and has to much tolerance to guide the chain.


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## Al1943 (Jun 23, 2003)

Kontact said:


> Considering that WD40 dries leaving a waxy film, I'd use something else. Spray Triflow works well for STI.
> 
> I don't think blasting out the factory lube is a good idea until the problem is actually shown to be an internal shifter problem.


There have been many many forum postings about shifter problems being cured by flushing out STI shifters with WD40. Adding a light oil afterwards may be fine or it may eventually create a greasy mess. WD40 is more likely all that is needed.


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## woz (Dec 26, 2005)

I'd suggest first trying to figure out if the problem is in the front or the rear of the bike. Easy test. 

1. Shift to the largest cog, (23, 25 whatever.)
2. Stop pedaling and shift all the way to the 11t. This should completely slack the cable.
3. Slip the housing out of frame at the rear of the bike so there is no tension on the cable.
4. pedal the bike and the derailleur should drop to the 11t.
5. keep pedaling and at the same time use your hand to carefully move the derailleur up the cassette and then let it go again while continuing to pedal.
6. watch the derailleur after you let it go. Does it go to the 11T? If it does go to the 11t does it go in one continuous motion or does it hesitate in the 12 before going to the 11t.

If it cleanly goes to the 11t you know the problem is not with the derailleur or hanger, but with the cable, housing or shifter. If it does not go cleanly into the 11t you know the problem is with the derailleur or hanger. 

Once you know if the problem is in the back half or front half there are other checks to help narrow down exactly where the problem is. If you post the results of this test I'll be happy to give you some others to help pinpoint the problem.


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## cxwrench (Nov 9, 2004)

woz said:


> I'd suggest first trying to figure out if the problem is in the front or the rear of the bike. Easy test.
> 
> 1. Shift to the largest cog, (23, 25 whatever.)
> 2. Stop pedaling and shift all the way to the 11t. This should completely slack the cable.
> ...


^this^ is some good solid advice.


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## aclinjury (Sep 12, 2011)

cxwrench said:


> ^this^ is some good solid advice.


+1 on that


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## Wheelman55 (Jul 10, 2009)

A set of new SP41 cables might do wonders for your shifting as well.


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## OldZaskar (Jul 1, 2009)

woz said:


> I'd suggest first trying to figure out if the problem is in the front or the rear of the bike. Easy test.
> 
> 1. Shift to the largest cog, (23, 25 whatever.)
> 2. Stop pedaling and shift all the way to the 11t. This should completely slack the cable.
> ...


Thanks woz. If my friend (who owns the bike) hasn't taken that bike to the shop yet - ^that^ is our next step. Regardless, I'm keeping your 6-step test in my bag of tricks for next time. Thanks.


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## arkitect (Apr 25, 2011)

So....... did you figure out a solution yet? I want to find out what the answer is!!!


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## OldZaskar (Jul 1, 2009)

arkitect said:


> So....... did you figure out a solution yet? I want to find out what the answer is!!!


Hoping to get to it tonight. Will report back.


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## aclinjury (Sep 12, 2011)

I know it's been over a year, but did you figure out the solution??
I'm having similar issue.


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## OldZaskar (Jul 1, 2009)

I never got a good answer. My friend took the bike to the shop before I could try again. I asked what was up with it. He didn't know (or care) enough to get a detailed description of the cause/fix. He didn't need any new parts though. My only take-away is that as good as I think I am working on a bike... I'm no pro. Not even close.


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## echo7 (Sep 7, 2010)

OldZaskar said:


> Shifts crisply and quickly through the other 9 cogs. But will not drop into the smallest cog... well, 1 out of 4 times it will after about 10 pedal rotations and a lot of chatter. Or, if I manually "nudge" the derailleur, it'll drop down. Here's what I've tried to rectify the issue...
> 1. Adjusted limit screw - actually dialed it out so far, I took the screw out.
> 2. Replaced the cable and housing
> 3. Made sure the loop is not too tight - it's actually, bigger than the other bikes I compared it to
> ...


this happened to me before and the problem was the plate(holding the cable) is oriented the wrong way preventing the der to drop to the last cog.. but seems like you quadruple checked it.. Ill take a picture and post when I get home...


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