Problems with DA 7800 shifting accurately

Discussion in 'Cycling Equipment' started by 886014, Mar 18, 2010.

  1. 886014

    886014 New Member

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    G'day guys, this one is driving me nuts so I thought I'd throw it out there to any experienced workshop guys to have a crack at.

    Basically it's a bike with 7800 DA, pretty conventional. I'm having problems with consistent shifting on the rear derailleur so if I adjust the cable tension so it shifts up to a lower gear (ie larger sprocket) ok, it won't shift back down again. It seems to be having most problems around the middle of the cluster, with non-linear shifting.

    So far I've checked and adjusted the hanger alignment, cable path (I accidentally once put a cable on the wrong side of the securing bolt and that leads to non-linear shifting incidentally), cable friction, checked the cable (sometimes if strands come off they can hang up in the STI), swapped wheels, and even resorted to swapping out the rear derailleur for another used one. All made no difference.

    In desperation I've thrown a heap of spray lube into the STI and it seems to have improved it, but because it's all a bit finicky I hope I'm not kidding myself. Now it SEEMS to shift better down to a higher gear but still isn't quite right going back up to larger sprockets. This has me stumped, but it feels as if the large shift lever moves across and "clicks" but possibly isn't pulling the cable sufficiently, it also doesn't seems to consistently shift 3 gears if the large lever is moved all the way across.

    Swapping out pretty much everything on a bike is dead simple with the exception of the STI levers, so before I start unwrapping things I thought I'd throw it up on the board. I don't know how many kms these levers have on them, but it could be as many as 25,000km. I'm wondering if others have come across a similar symptom with either worn or faulty STIs?
     
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  2. Peter@vecchios

    [email protected] New Member

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    As you mentioned, start with cables and housing(I recommend 5mm der housing). Also ensure the under BB guide is clean/smooth. Spraying the shifter innards is next. If it still isn't working, the shifter could be on it's last legs.
     
  3. alfeng

    alfeng Well-Known Member

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    FYI. The rear derailleur's spring returns the cage/pulleys to the smallest cog (except on Rapid Rise rear derailleurs where it is the spring moves the cage in the opposite direction).


    You can confirm/isolate that the shifting problem is-or-isn't with your cables & housing if (with the bike in a stand) you:
    • remove the chain
    • detach the cable
    Then, manually, move the rear derailleur inward to the largest cog AND if it returns to the proper alignment with the smallest cog when you release the rear derailleur, then the problem is with your cable housing and/or cables.

    BTW/FWIW. I used to observe a similar problem on occassion with my Ultegra 6500 & 6501 shifters BEFORE I switched to Campagnolo shifters ...

    Okay, before switching to Campagnolo shifters, I deduced that the problem [which I was experiencing] was apparently due to the housing ...

    Consequently, I prefer to use BRAKE CABLE HOUSING rather than the smaller ID, parallel stranded Derailleur Cable Housing which Shimano & Campagnolo seem enamoured with ...

    Housing changed ... no subsequent problems.

    Coincidence?

    Maybe.

    Maybe not.

    I still have/use some of that parallel stranded housing, but I only use it because I have it and I'm too frugal to throw it out ... I treat the parallel stranded housing as a ticking bomb.
     
  4. 886014

    886014 New Member

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    Hi Alfeng, thanks for replying but I'm afraid I don't at all follow your logic. Obviously with no cable attached the derailleur will sit on the limit screw, unless there was something physically preventing that from happening. Even if that was the case it would would manifest itself in being unable to get the 11 (my favourite excuse for not winning a sprint btw :D ). While I admire your confidence, I feel there's one component you haven't mentioned at all, the STI levers as they're increasing looking like they're the culprit.

    I don't share your disdain for the Shimano recommended gear outers and have put countless sets on bikes before now. I guess I'm old-school in thinking the manufacturer probably knows a little about their product, hence why they have different specs for brake versus gear cable sets. However they do indeed wear and are sensitive to excess friction so it's probably not a big dear to drop another set in there before I dismiss that area. I couldn't feel any significant friction when pulling the cable by hand, but it wouldn't do any harm to change them anyway.
     
  5. Peter@vecchios

    [email protected] New Member

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    Use 5mm der housing and it will shift even better than brake housing.
     
  6. alfeng

    alfeng Well-Known Member

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    Did you want me to reply?

    OR, were you just reenforcing what now appears to your own, prior decision to justify to someone (yourself OR someone who shares your bank account) the purchase of a new pair of shifters?!?
     
  7. 886014

    886014 New Member

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    Alfeng, I'm not quite sure if you're trolling for an argument but I'm sorry to say you won't get one out of me. Your post stated "FYI" and the most basic observation of how a Shimano rear derailleur operates. Thank you for that "information", like I'd never seen one before :rolleyes: You're free to post what you like, but if you want to piss off an experienced mechanic state the obvious to him like he wouldn't know.

    You then went on to state you'd need to remove the chain, quite why you'd break a chain to work on a shifting problem is quite beyond me, but feel free to do whatever you like. Personally I'll choose to just remove the wheel, but hey, maybe that's just me. Followed was a process to check the adjustment of the limit screw and a statement that if the limit screw was in adjustment then the problem was in the cables. That's certainly an interesting conclusion. I'm not sure of your setup, but on this bike the rider doesn't pull cables with his teeth, there is a set of shifters hanging off the front that can also cause problems. The fact that after they were lubed the shifting seemed to get better definitely seems to focus attention on them. Most of the problems I've had with shifters in the past have been quite different to this, hence I'm not convinced and why I posted the question on the board.

    Rather than beginning your post with a statement of the obvious as if you're addressing an imbecile you ACTUALLY meant to post something along the lines of "I once had a similar shifting problem that was cured by changing the outer cable housings", then you may have received a somewhat more enthusiastic reply. The bottom line is you have a very valid point and I really am grateful that you took the time to try to help. But imagine how you'd feel if you went to a garage to have your car serviced and the first thing the guy does is lean across the desk and say "For your information, you start the car by putting the key in the ignition"
     
  8. alfeng

    alfeng Well-Known Member

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    Hey, I was just trying to expedite your trouble shooting ...

    The way you had posed your post it seemed as though you were energetic but clueless ... even your most recent post (above) indicates you are actually clueless in some regards.

    I'll now presume that you just wanted people to tell you that you needed to replace your shifters rather than $40 +/- worth of cables and/or housing.

    Best of luck.
     
  9. 886014

    886014 New Member

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    Like I say mate, if you're a troll, good luck to you. I have repeatedly stated that I am not certain where the problem lies, however the fact the problem became significantly better after lubricating the shifter tends to suggest the problem MAY be up there, it MAY also not be. I very much doubt it, but the logic is tending to suggest it MAY be worn to the point it's affecting the shifting. No I don't want to replace the shifter, as I'm sure those who are semi-literate would clearly see from my posts, and why I put it up in the first place! I was, however, interested to find out if others have had similar problems with shifters.

    Your post clearly indicates you know little or nothing about bikes and just happened to get lucky on a bike once. Over a coffee I read through some of your other posts on this BB and was horrified by some of the "advice" you were dispensing. Replacing the outer cable is, however, an excellent idea, and cutting a bit off a roll and throwing it on certainly wouldn't hurt. The cable friction felt fine to me but what the heck; I'd make the most of the gloat if I were you. However the price you quoted for a metre of cable housing gives the game away mate, you're a hubbard who wanders into bike shop with NFI what he's crapping on about, I meet people like you every day, but because he has nothing better to do with his time, hangs around a BB declaring himself an expert. Your method of "diagnosing" was completely flawed and proved nothing other than you were lucky, and by your own admission you still don't know if what you did was just a coincidence. I pointed out why your methodology really didn't prove anything, both for your interest and others who may later search the BB with a similar problem. Meanwhile you retort by claiming I'm "clueless". Since I have absolutely no interest in precisely why you say that, to answer your question
    the answer is a definitive NO, not particularly, troll elsewhere. Thanks for the luck, likewise, have a nice life.

    Edit: Can I suggest when posting you try the "reply" button instead of the "quote" button. Most people are quite capable of reading prior posts without the whole lot needing to be repeated ad infinitum
     
  10. kdelong

    kdelong Well-Known Member

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    I have had a similar problem with Ultegra and as Peter suggested in his first reply, check your cable guide on the underside of your bottom bracket. In my situation, the cable had worn a barely visible groove and was intermintenly catching in it causing balky shifting. It took me three weeks to find it, but after I did, it was a $1.50 repair.
     
  11. alfeng

    alfeng Well-Known Member

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    REALLY?!?

    I was going to let it drop ... but, FYI, others who may have a similar problem (now, or in the future-or-past) or who are simply curious read many posts in this Forum ... we can't all be as parochial or narcissistic as you to presume that the world revolves around you and that you, as the OP, are the only person reading the thread.

    So, you claim you are a mechanic of some sort ... OR, did I mis-read that?

    I'm glad you looked at your derailleur, etc.

    But, if you truly understood how your shifter functioned, then you would address the connection between the shifter & the derailleur AFTER you assured yourself that the derailleur's motion was not otherwise impeded. NOT because I say so but because that is how trouble shooting is done (well, that's how 'I' do troubleshooting -- I look at the simplest possibility, first, and progress from there -- so, maybe it is because I say so if everyone else looks for-and/or-at the most complex possibility, first!).

    Regardless, how you can know that the rear derailleur's stops are set properly without a hub-and-cassette in place are beyond me ... so, you're indeed one-up on me there. Kudos!

    I was going to elaborate (for others) how a shifter functions, but for you I'll just say that if your shifter were worn in the manner you seem to be suggesting, then the rear derailleur would probably be SLIPPING the chain from larger cog to smaller cog when you didn't want it to rather than being sluggish in moving down to (only?) the smallest cog. Because it is only occurring between the second to last cog and the smallest cog suggests (to me) that the problem is NOT inside your shifter.

    If your shifter's problem were manifesting itself throughout the shifting range OR sporadically throughout the range AND you had eliminated the lesser possibilities, then it could be possible that there might be a problem within your shifter's mechanism.

    Again, good luck.
     
  12. 886014

    886014 New Member

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    Mate, can I sincerely suggest you RTFQ PROPERLY before hitting the reply button. I didn't think it was necessary to state the bleeding obvious, but for your benefit, yes a normal alignment process WITH THE WHEEL IN PLACE (as it always is) was done, both initially and when the derailleur was replaced. How could two derailleurs be identically impeded? So much for your extraordinary logic! As I suggested in the very first post, the normal process of confirming alignment of the hanger and typical "gotchas" was conducted. Operation of the shifter, cable friction, etc can simply be done with the wheel off. There is NEVER a need to break and remove a chain (as you suggested) to work on the shifter, the lower cage bolt can be removed and the upper one loosened to drop the lower pulley out. But of course you would know that. Or maybe not.

    Again, you clearly don't know what you're talking about. You've been busted as somebody who masquerades as an expert but in fact has NFI. I see no point in pursuing any further conversation with you, and will let you get back to dispensing other "excellent advice" like telling people to wipe oil off their frames with paint thinners, let's hope nobody reading THAT gem of yours has anything other than a powdercoat on their frame :eek:
     
  13. alfeng

    alfeng Well-Known Member

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    REALLY?!?

    Oh, this is so interesting ...

    But, I suppose it's your prerogative to try to disparage me because I don't have a problem indexing my shifters the way you have ...

    I don't worry about a rattle-can paint job on my bike ...

    Was there something else?

    What kind of "mechanic" are you supposed to be?
     
  14. 886014

    886014 New Member

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    Troll elsewhere mate, nobody here has any interest in what you have to say
     
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