scottmcd

I have a 105 Ultegra rear derailleur 11 speed group set at first was 11-32 and was changed to 11-34. When my bike was new I was able to get it to shift fine but as things wear I am having issues with the low gear. I was looking at R8000 and was wondering if it would work as a replacement.

Andrew R Stewart 

Gee, so much could be going on that has nothing to do with your 105 Ultegra rear der. Has anyone with diagnostic skill had a chance to look at the bike? Andy

dsbrantjr

+1 It could have more to do with the larger low cog and/or cable/housing wear than needing a new derailleur. Have any adjustments been attempted?

dedhed

105 and Ultegra are 2 different things

ljsense

Turn the B adjustment screw in (clockwise) one revolution and unscrew your cable tension barrel half a turn, and I bet it will work fine.

The B adjustment screw sits alone and faces backward, relative to your bike, like it's looking down the road where you've already gone. Its screw end touches your derailleur hanger at the dropout.

The cable tension barrel is probably black with ridges on it. Put your fingers on the rear shift cable by the chainstay. Slide them toward the derailleur. It is the last thing you'll touch before you get to the derailleur.

scottmcd

I have had this at my local bike shop the adjustment does not hold works fine on the flats. The derailleur specs are 11-32 I changed the cassette to 11-34 it rode real good for a couple thousand miles and Started giving me issues jumping back and fourth between my 2 low gears really bad on hills I have had new cables replaced and everything else gone thru.

Andrew R Stewart 

B pivot spring tension loss, bent hanger, bent cage, worn guide pulley bushing, cable stuff (including BB guide wear), cog teeth or chain link damage, hub/cassette location is shifting, broken axle, and other causes are possible. After going through the list try another wheel with a in spec cassette. This kind of goose chase is where a relationship with a LBS can really help. Not just from their greater range of experience but also they have resources (other bike's parts) to try. This is a good off season job, when time is "worth less". Andy (who knows that 105 Ultegra stuff is really one or the other, but felt it best to not point out the obvious mistake and try to help with the actual problem).

scottmcd

Look all the things you have mentioned have been either changed out or checked, my bike is well taken care of maintained. I have a new chain new bearings in my rear axle new cassette. The only thing that has not been changed is the derailleur. with 5000 plus miles on the bike seems to me because I have stretched the limits of my 11-32 derailleur for so many miles I would like to get something that fits the cassette that I want to run. I am out of specs on my derailleur, that is why I want to change to something that will work. I really appreciate all the tips, IF I was wanting to keep my current setup I would just go back to the 11-32. Living here in the Seattle area with a lot of climbing the 34 comes in very nice!! I am just asking aa simple question, if someone knows if this will work or not. Again I thank everyone for their input!!!

terrymorse 

Shimano RD-R8000-GS rear derailleur is 11 speed and is rated up to 11-34 cassette size.

No reason why it wouldn’t work as a replacement.

jimc101

105/Ultegra are meaningless terms for this type of question, you need to give the specific part number, ie. RD-5800 or RD-R8000 preferably with SS or GS spec known as well for any answers

So, it worked fine with the 11-34 at the begining? no mention anywhere about the cables, could it be as simple as they either nede adjustment, or more likely replacment?

Kapusta

First, there is no “105 Ultegra” RD. 105 and Ultegra are two different models of Shimano RDs.

I would give a roughly 2% chance that the issue is the derailleur itself unless you see some actual damage. Outside of replacing jockey wheels, something like a 105 (or Ultegra) really does not wear out. At least not for a long, long time. I’ve never worn out a shimano RD.

A bent hangar is what i would suspect. You say it was checked..... how? Did someone use the proper tool, or did they just eyeball it?

Someone else gave a long list of causes more probable than a “worn out” derailleur. I agree with that list.

However, if you are really determined to try a new RD, the GS version of the one you listed will work (or may be the one you already have).

Marcus_Ti

It is a simple question...with all the needed data points. Which we don't have.

WizardOfBoz

The simple answer to the question "Will my shifting work properly if I upgrade to an Ultegra derailleur?" is not answerable from data we have. Here's why:

1) Your 105 worked fine for a while and now doesn't. We don't know why and it's hard to infer with what info we have.
2) When an RD stops working well, it is almost never the RD itself (jockey wheels the rare exception). So experienced mechanic's skepticism is that it won't be the RD.
3) If the issue IS outside the derailleur, swapping to an Ultegra derailleur likely won't help. You'll spend money and the issue will remain.

Here is a question that CAN be answered:

Is the Ultegra R8000 derailleur compatible with my setup? Answer: Almost certainly. I have that RD, and it works great.

If the problem isn't within my current 105 RD, will changing the RD improve shifting? Answer: Maybe. Probably not. The R8000 is terrific, though, and if you still have shift problems, you can rule out derailleur malfunction (but not adjustment). That said, in installing the new RD you may find - or even inadvertently fix - the underlying issue. So you install the new RD and discover that your chain has been too short. Or that the hanger really is bent. It's kind of faith-based bike diagnostics to plow forwards though.

What other options do I have? Answer: Well, your concern about using your current 105 outside specified range is valid. You could consider going to a long-cage 105 derailleur, which has a tooth spec of up to 39t. There Ultegra is not quite twice as expensive (about 97 vs 56 bucks, interweb pricing). Now I'm a gear snob (since buying my custom all Nuovo Record Paramount back in the day) so I always try to go for the best affordable gear. The Ultegra is just about the best performing stuff around. But 40 bucks is 40 bucks.

Wilmingtech

When you put the larger cogset on, did you resize the chain for the larger cogset?

-Sean

Kapusta

I But that is not the question he is asking.

The OPs question is straightforward and there is a straightforward answer for which we have the needed info to answer. Further the correct answer has been given: The RD he is asking about can be used as a replacement for the one he has, and the version with the GS cage will clear a 34t cog.

Whether this will actually fix his problem was not part of his question, and he has made it abundantly clear that he’s not interested in having that part addressed.

scottmcd

Thank you! I did add confusion with the 105 / Ultegra. I got the specs off the website of my bike a Kona Esatto DDL I have a 105 front derailleur and a Ultegra RD you guys that you drought I had anything changed or checked you are wrong!! all components (except the RD) were either changed or checked (the hanger was changed and made no difference). What most of you failed to see is that the Ultegra I am running is only supposed to handle a 11-32 cassette which I stated. I have been running a 11-34 which maxes out the adjustment in my Ultegra. Yes my chain has been lengthen to try to help with the 34T. As I said earlier the adjustment only holds for a short time. My LBS wants to sell me a $400 derailleur the brand and model I do not remember, I am looking for another option that why I asked the question. I am taken back at the criticism and negative feed back you get for a simple question...….. Once I install my new RD I will post my findings, maybe it is something else we shall see...…. I just want to ride...… don't you??

cpach

All 11 speed Shimano road rear derailleurs are cross compatible (also, unofficially, Tiagra 4700's rear derailleurs) so R8000 will certainly work. It'll work better with the 34t, but generally speaking exceeding capacity by 2 teeth usually works reasonably well. Rear derailleurs CAN be the cause of shifting issues--most commonly some part of the cage is bent, but also it is possible for the pivots to develop sufficient play or friction that it effects shifting significantly. As a mechanic, I'd probably look to see if the derailleur looks to be running parallel to the cogs and if there was excessive play. If the derailleur looked/felt OK I'd eliminate all other possible variables first.

Also an important point is that changing the derailleur hanger does not alone mean its straight. There are tolerance issues with frames mounts for hangers--I always check with a hanger alignment tool even with a new hanger, and have frequently needed to straighten new hangers (or to remove paint/other imperfections from its mount).

Kapusta

As mentioned above, exceeding the stated RD cog capacity by 2 teeth is usually fine. But more to the point, it will either clear the big cog or it won’t. If it does, then the cog is - in reality - within capcity, and you are not in any way harming or prematurely wearing the RD. If your bike shifted fine to start with, than you were not actually exceeding its capacity, and I can’t see how it could have anything to do with your shifting issues now.

Also, I think you mentioned 5000 miles. That is not enough road miles to wear out an RD unless you are in some very unusual conditions which would have likely trashed many other parts of you bike first..Therre may have been some defect in this particular RD that lead it to wear so fast. But it was not a cog capacity issue.

Or it may have gotten damaged. It does happen, though usually that is apparent by looking at it.

WizardOfBoz

I would argue that the OP's posts are not unambiguous at all. You yourself had to point out to the OP that there's no 105 Ultegra. The OPs first post said essentially "I have a 105 RD, and I swapped out 32 T rear cassette for a 34T. It used to shift ok, now it doesn't. Will an Ultegra RD work as a replacement?".

If the OP didn't want suggestions about shifting malfunction, why did he inlcude this information? Why not "I changed my casssette from a 32 to a 34T. Can I swap out my current 105 RD for an Ultegra?"

If your point is "answer the question", then we agree that the OP has a response. If your point is "only answer the explicit question", when has that rule EVER applied to BF? Or any other forum? Further, one reason folks write in here is to get expertise that they don't have. I'd argue that's its downright anti-social and mean to let someone asking for help to fail.

At my first post-college job I worked designing control systems for a large nuclear facility being built. I was specifying a pressure transmitter and had located a make and model that I thought was suitable for the application. I asked my colleague an explicit question about the range. "Will 0-100 inches of water column be appropriate for the Acme Model number 100 transmitter ranges, George?" George was about 50 and was a top engineer, and a nice guy. He responded "That transmitter won't work". Not what I asked. I responded with a list of things I'd looked at that suggested to me (an engineer with a new degree but with 1/30th of George's experience) why the Acme 100 transmitter WOULD work. We want back and forth, me giving what I thought was a substantive defense of that make and model. George telling me it wouldn't work. Finally I asked George WHY the thing wouldn't work. "I could explain the details to you if you want, but I designed that transmitter when I worked for the transmitter company. My name is on the patents for that transmitter. I'll ask you to trust me when I say that it won't work in that application". Oh. If George had said "yeah, that range is fine", we would have purchased about 20 million dollars worth of the wrong product (the facility was three buildings, each the size of three football fields, and had 150,000 50 HP machines running 24/7 - a lot of HVAC). So, my point is, sometimes its inappropriate or even downright wrong to just answer a question as asked. Even if the idiotic, headstrong engineer is trying to insist that you answer the explicit question.

Kapusta

105 or Ultegra.... same answer: the RD he is looking at in the GS version will work as a replacement.

WizardOfBoz

"... provided the underlying issue affecting shifting is fixed. Else, it likely will not 'work' any better than the 105 RD."

Kapusta

IBy this logic, no question of “Can A work as a replacement for B” can ever be answered.

WizardOfBoz

Good heavens, you're not giving up, are you? Ok, I won't either.

There is always a context, of possibly variable relevance, to any question. Examples:

"I'm trying to find where to get a small quantity of West Systems' G-Flex epoxy. Recommendations?"
---> Context not specified. No problem, answer the question.

"My plastic headlight bracket broke. I'm trying to find where to get a small quantity of West Systems' G-Flex epoxy. Recommendations?"
---> Context speciifed. May be relevant. Best to address the implied context. "Epoxy likely won't work on most headlight brackets. Recommend a new bracket. Or, buy that epoxy at StickySystemsInc.com".

"My 853 steel frame broke at the bottom bracket. Can anyone tell me where to buy West Systems G-flex epoxy?"
...> Context specified and relevant. Answering the question without qualification is highly irresponsible and might even be construed as incurring liability.

The OP specifically stated that their shifting had been working and now didn't, and asked whether the Ultegra could be used as a replacement. This sequence created an implied correlation (at least in the mind of just about every other person posting here, I presume). To answer without addressing that implied correlation is really non-responsive and pretty negligent. Furthermore, BF threads form an archive, and others reading this thread later would probably be helped by the answers given. "Gee, I guess if my RD stops shifting nicely, buying a new RD isn't the default option". So even if the OP says "no, no, I just want to know if the Ultegra is compatible" I view it as irresponsible and pretty mean-spirited to say "Sure! Knock yourself out!". Especially when we're talking about a $100 derailleur.

I understand the proverb about leading the horse to water. But in BF threads, the path you make leading that first horse (that doesn't want to drink) will be used by other horses that are thirsty.

Andrew R Stewart 

To the issue of what question various repliers answered, imagined or explicitly asked- If you asked your PCP "I have a pain in my leg that makes me limp, I didn't have it before. I have tried (fill in the blank here with stretching, OTC pain meds, orthotics, physical therapy or more non evasive stuff) with no improvement. What replacement knee do I need?" It would be very wrong for him to prescribe replacement knee X without doing his own review of the situation. Why should this forum be any different in our approach? Andy (who has 2 Dr.s in the family)

scottmcd

I don't have any bent or damaged parts anywhere on my bike period! I have never put the bike down, and like I said WELL maintained. The whole drivetrain has been gone thru, I believe I said earlier I have changed everything EXCEPT the RD. It shifts like a dream except for the 34T gear it jumps down to the 30T when going up a hill then still try's to get back to the 34T. No matter how times its adjusted it goes back to giving me issues. Like said I will let you all know how it turns out as it can be a learning experience for all. Especially for myself!