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This has stymied a few mechanics

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This has stymied a few mechanics

Old 11-01-18, 03:23 PM
  #26  
Andrew R Stewart 
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Originally Posted by velorider562 View Post
If the shifting gets worse between the higher vs lower gears, then it might be the lower limit screw. The cable tension ensures the derailleur moves a fixed amount, but if the starting point is not correct by the time the derailleur gets to the larger cogs the derailleur is off by a small amount. Try unscrewing the lower limit screw a half turn and see what the impact is.

The lower limit screw is frequently neglected but is critical for precise shifts.
I don't see the truth in this. The limit screws say nothing to the shifter's indexing points, that's the cable's length (or as most say "tension"). One can have all but the small or large cog shift perfectly well, on index as it might be said, but have the last position not so well as that limit screw might be too far in and limit the der's travel ONLY at that point.

Related but a side bar is the many bikes I see that have had the low gear limit controlled by the shifter because that low gear limit screw was too far out. It then is only the shifter's travel that keeps the chain from over shifting into the spokes. It seems that many assembly mechanics don't know how top move the ders without relying on the shift levers. They think if the der stops when the shifter did the low limit must be correct. They will be wrong and that bike's rider won't likely ever know the bike was adjusted wrong till the chain goes too far because a shock or force came along that was there when the bike was on an assembly stand. Andy
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Old 11-01-18, 04:08 PM
  #27  
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Originally Posted by velorider562 View Post
If the shifting gets worse between the higher vs lower gears, then it might be the lower limit screw. The cable tension ensures the derailleur moves a fixed amount, but if the starting point is not correct by the time the derailleur gets to the larger cogs the derailleur is off by a small amount. Try unscrewing the lower limit screw a half turn and see what the impact is.

The lower limit screw is frequently neglected but is critical for precise shifts.
Even if this was the case it would be the high limit screw not the low limit screw...but this is not the issue as it is not that the derailleur is not indexing properly it is an issue with it not shifting smoothly through the range....there is indicative of an alignment issue or a stick-tion issue.

-j
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Old 11-02-18, 04:52 AM
  #28  
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Originally Posted by Koyote View Post
Good idea, and cheap.
Yes absolutely try replacing the cable housing (and just use another new cable while you're at it).

My experience is that the cable housing, especially the loop from the chainstay to the rear derailler, gets gunked up or rusty and created enough friction that it effects the shifting in exactly the way you're describing. New housing, new cable, nice crisp shifting.

The other thing to watch with the cable housing is that you don't kink it anywhere (even slightly...once it's kinked you can't ever remove that even if you think you've straightened it) or cut it too short so it has to bend too quickly. Both situations can also create enough friction between the housing and the cable to cause poor shifting into the higher gears as well.
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Old 11-02-18, 10:11 AM
  #29  
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As you're replacing the cable and housing, don't forget to change the Teflon tubing under the bottom bracket if you have externally-routed cables. That tubing is a grit magnet.
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Old 11-02-18, 10:13 AM
  #30  
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I'm still wondering how any bike mechanics could be stumped

by sluggish shifting where years-old cable housings had not been replaced.

Wouldn't this be like number 2 on a diagnostic list?
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Old 11-02-18, 10:15 AM
  #31  
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To be fair he didn't say good mechanics.
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Old 11-02-18, 10:24 AM
  #32  
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Are you sure you have a 10 speed chain fitted? A chain for say a 5 speed (extreme example) is much wider on the inside. So as you're shifting down, the shifter has to give more slack to enable it to drop.
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Old 11-02-18, 11:57 AM
  #33  
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I had a similar problem. My problem occurred because the RD wire, in haste, was not connected correctly at the clamp screw.
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Old 11-05-18, 03:12 PM
  #34  
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I agree that it sounds like cable/housing drag and they should be replaced. Typically the rear derailleur spring is under higher pressure as you move it to lower (larger) rings. This would be why the first indication of a cable drag issue is that the derailleur will not go down onto the highest gears (smallest ring).

Once this starts happening cleaning and lubing the cable and housing is just a stop gap measure as usually the inside of the housing is worn.
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Old 01-03-19, 09:11 AM
  #35  
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My riding season is mostly over now, so I've had time to work on this and thought I would report back to the thread. Bottom line: problem still not solved. Here's what I have tried:

--New cables and housings.
--Shifter sprayed out with degreaser and then with copious quantities of lube.
--Derailleur thoroughly cleaned and lightly lubed.
--New Derailleur hanger. (I had a spare, figured it couldn't hurt to try it out.)
--Derailleur adjusted - L and H limit screws and B screw. Not much gap between jockey wheel and largest cog (32t) with B screw at its limit, but they are not touching.
--Derailleur and cassette have already been replaced earlier in the year, and made no difference to the shifting.

Shifting is still weird. Shifts fine moving down the cassette until about the 6th cog, then it doesn't want to drop onto the 7th cog, and also balks at moving from 7th to 8th cog. Balks when moving up the cassette from 8th to 7th cog and from 7th to 6th cog, too. Shifter is moving cable, RD moves, but it seems like the RD doesn't move quite enough.

At this point, I am thinking that the shifter must have a problem...And that is a bummer as it is expensive. Unless the BF brain trust has any more ideas?
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Old 01-03-19, 09:55 AM
  #36  
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Pictures of setup and list of parts by name/number wouldn't hurt. Also weird things I'd check would be:

Cable housing routing, doesn't matter if it's new if it's the wrong length. Common mistake to replace the exact length it used to be when it could be causing issues. Not sure if you mentioned road bars with taped over housing, I always suspect the taped over housing as it's been under there for awhile and could be seated poorly in the shifter. Same with internal cables/housing, who knows what's going on in there.

Derailleur B position screw, try other settings. If it shifts horrible no harm in cranking it way out, I have several bikes that shift way better like that for no reason. Although I suspect it has to do with the actual position of the hanger.

Cassette lockring torque, probably not an issue, but worth checking. Also derailleur hanger bolt/bolts and rear wheel quick release. I have a mountain bike that only maintains a calibrated hanger alignment for a given QR tightness, if you pull the wheel and change how tight it is the hanger moves a surprising amount.

Frame and size? Chainstay length? I've encountered a bike or two with chainstays so short they seemed to exaggerate chainline issues and had constant phantom shifting issues. Usually more of a front shifting thing, but anything is possible.
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Old 01-03-19, 10:31 AM
  #37  
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Originally Posted by Koyote View Post
That occurred to me, but the problem started when the Ultegra shifter had <10k miles. Do they really crap out that young?
Yes. Sometimes. One problem is the grease gets thicker over the years. Not even miles used in some cases. The most common fix to this problem is flushing the shift mechanism with spray, like wd 40, silicone spray etc. Then let it drip for a while and put some silicone spray in and let it sit a couple of days before riding. There is plenty of info about this on line. Put your bike in the bike stand vertical with the front wheel at the bottom, so that the brifters will drain to the floor, not the handlebar tape. As you spray shift up and down too. I've done a few. Three of my own bikes. One method I have not tried, but sounds really good I taking the brifter off the bike and soak it submerged in oil. Probably someone will post their experience with this.
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Old 01-03-19, 10:37 AM
  #38  
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I believe you mentioned you are using Ultegra brifters....I don't recall seeing anywhere what rear derailleur you are using. Can anyone weigh in on whether there were any cable pull length changes made during the Ultegra 10 speed component era?

When you changed your housing did you lengthen the loop from the chainstay to the derailleur? to short can cause friction/shifting issue....with higher number of gear systems this loop should be longer than that which would be correct for 8 speed and below. So if you started wrenching years ago this is one area to investigate.

Is your rear derailleur itself bent? this can mimmick a bent hanger

is the cable routed to the cable anchor bolt correctly? Routing above vs below the bolt can make a difference.

Some photos/video might help.

if you PM me, perhaps we can use skype to set up a video conference call and discuss further.

-J

Last edited by Greenfieldja; 01-03-19 at 10:41 AM.
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Old 01-03-19, 11:30 AM
  #39  
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Originally Posted by Elvo View Post
Ultegra 6800 is known to chew up cables at the shifter and have some of the strands get stuck in the mechanism.
This is a point I'd follow through on (especially since you've checked everything else). I have a Dura Ace 11 speed, and it chewed up a cable. A chewed up cable could be causing stiction/friction or jamming. I'd remove the shift cable from the brifter and check to ensure that there are no bits of wire or grit in the brifter mechanism. I'd take a new cable, insert it into the brifter, and manually shift it to ensure that the cable moves with each shift, with minimal pulling force. That is, keep a little bit of tension on the shifter with one hand, and shift the lever with the other. The cable movement should be immediate and certain. If not, fix or replace the brifter.
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Old 01-03-19, 11:36 AM
  #40  
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Q&D "divide and conquer" approach. If you can reproduce the problem at will, as it's happening, pull downward (toward the der) on the cable along the downtube.

If it still doesn't grab the next cog, then I would look "downstream" for the problem -- derailleur, lower section of cable housing at the der, poss. even the guide underneath the BB shell.

If it DOES shift with that tug, that suggests the problem is "upstream" -- top section of cable housing, shifter, etc.

That should at least narrow the range of possible culprits.
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Old 01-03-19, 11:45 AM
  #41  
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Quite possibly an Operator Error of some sort.
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Old 01-03-19, 12:23 PM
  #42  
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For some reason, Shimano is very very sensitive to the position of the "B Screw". Try loosening the B screw to allow the derailleur to swing forward a little bit. Even 7-8 mm is a big difference in shifting.

very good tutorial (section 5)

https://www.parktool.com/blog/repair...eur-adjustment

Last edited by Reynolds 531; 01-03-19 at 12:28 PM.
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Old 01-03-19, 12:56 PM
  #43  
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Sounds like a pretty frustrating situation. Given that you've tried all of the right steps to solve the lack of movement that allows for release of tension in the shift cable, it's time to try some oddball stuff. If you have a spare wheel and cassette, I would experiment with swapping them for your current setup. There's an outside chance that you've got a worn cassette, which could include a crushed spacer between the smaller cogs (they are plastic), and it's also possible that you have something going on with your rear hub that is allowing the cassette to move around when you shift.
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Old 01-03-19, 01:31 PM
  #44  
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Originally Posted by trailangel View Post
Quite possibly an Operator Error of some sort.
Yes, because brifter operation is so baffling.
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Old 01-03-19, 01:39 PM
  #45  
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Haven't read all the other replies, but, are you absolutely sure you have a cassette with the correct number of cogs. It must the same as the shifter is designed for.
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Old 01-03-19, 02:32 PM
  #46  
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Make sure that the derailleur cable path out of the shifter is the "straight" option. There are two cable paths possible for the RD cable. Choose the one that lets the cable go behind the bars - The bends inherent in the other path are more severe than necessary.

You should be able to pull the hood up and see which path is used. Let me know if you need a photo or for me to explain better.

Also make sure that you are using a road RD or a 9 speed mtn RD. If you are using a mountain 10 speed, the pull ratios are not right.
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Old 01-03-19, 02:36 PM
  #47  
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Also make sure that your cable guide under the BB is clean. You'd be surprised how much a little dried sports drink can gum up that guide.

I always put a dab of grease in the channel for the cables.
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Old 01-03-19, 02:49 PM
  #48  
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Originally Posted by aggiegrads View Post
Also make sure that your cable guide under the BB is clean. You'd be surprised how much a little dried sports drink can gum up that guide.

I thought I was the only one who ever had that happen.
I couldn't believe it when I finally figured out what happened.
(It was a homemade maltodextrin/fructose mix).
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Old 01-03-19, 05:26 PM
  #49  
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Had exact same issue as OP once. Turned out to be a shifter cable that was too stiff.
Look at the angle the cable has to make when exiting the barrel adjuster to the cable fixing bolt WHEN IN THE 11 OR 12 TOOTH COG. An overly stiff cable will NOT release enough at that position(s) if too stiff. The RD has little spring tension in that position making it doubly worse.
Make sure to use a thinner supple cable and I bet you will be good to go.
The more supple cable will make the sharp bend just better enough to allow more cable release, drop in the 11, 12 cogs.

New design "shadow" type RD's eliminate this weird bend all together.

Good luck
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Old 01-03-19, 05:49 PM
  #50  
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Every item in the supply chain to the RD, including the RD, has been replaced with exception of the shift lever. Replace it and see what happens.
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