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  1. #1
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    Front Derailleur No Longer Shifts on to Top Ring after Servicing Bottom Bracket

    Earlier this fall I started a thread about how to replace the bottom bracket on a 1990 Trek 1400. Thanks to everyone’s help I was able to complete this simple project quite easily. http://www.bikeforums.net/showthread...ent?highlight= I ended up just disassembling the BB, cleaning everything, replaced the bearings (used loose ball bearings rather than cages but I did add the extra ball bearings), relubed with Marine grade waterproof grease and reassembled. Played with it a little to make sure there was no play in the cranks, but was not so tight as to drag and I was done. ….or so I thought.

    The bike sat for a while until I decided to ride it again a few days ago. Much to my dismay, the front derailleur now no longer shifts onto the top ring. The chain just jams between the top ring and the derailleur cage. The chain never catches on to the teeth of the top ring. Would anyone have any clues as to why this happening and what the solution might be?

    During the servicing of the bottom bracket I did not mess with anything else on the bike. The front derailleur is installed at the correct angle and the correct height. The derailleur cable and set screws are set correctly. If I manually move the chain on to the top ring, it shifts down to lower ring correctly. And naturally it all worked correctly before I serviced the BB. I just can’t get the chain to shift to the top ring without jamming against the top ring.

    My initial thought was maybe the chain line is not correct because the axle is asymmetrical. I have attached the data sheet for the bottom bracket: IMG_0003.jpgIMG_0004.jpg This looks to me that the axle is symmetrical. Correct? Could I have possibly put in the wrong sized bearings? Could the crank arms be either not tight enough or tightened down too far on the spindle? Does anyone have any clues where I may have messed up?

    Thanks for any help you can give me,

    Jim
    Last edited by jctexas; 11-20-12 at 10:03 PM. Reason: wrong word

  2. #2
    I let the dogs out AlphaDogg's Avatar
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    Tighten the cranks arms onto the spindle as tight as you can (within reason). It takes something like 35Nm to properly secure crankarms.
    http://i736.photobucket.com/albums/x...6at14619PM.jpg
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    intellect? we don't need so stinking intellect. this is the 41.
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    And this is why I don't ride aluminum frames... they will explode if I look at it wrong.

  3. #3
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    Assuming nothing else changed (not necessarily a safe assumption, but...) then I suppose the right crank is now outboard of it's original position by a millimeter or two. Possibly you didn't tighten it on the tapered spindle as much.

    In any case, have you tested the outer limit position, and the cable tension? Try this first.

    Try to shift by pulling the cable away from the downtube like a bowstring. If that makes the shift, your answer is a simple cable length (tension) adjustment. If you cannot shift by the drawstring method, back off the outer limit and try again. Repeat backing off the limit and testing until you can shift, then adjust the limit properly, and finish with the cable length adjustment.

    If you cannot shift by the bowstring method even with the outer limit backed off all the way, then something radical changed, so it's up to you to try to figure out what you did when changing the BB.
    FB
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    An ounce of diagnosis is worth a pound of cure.

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  4. #4
    Senior Member Bill Kapaun's Avatar
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    1. You need to learn what a derailleur hanger is.

    2. Assuming you are using the original parts and didn't do anything to the FDER, the only option left is that the crank isn't tightened enough to "pull" the rings close enough to the FDER.
    Else, your spindle isn't symmetrical and it's on backwards.

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    I have sort of verified the outer limit position and the cable tension; at least to the best of my ability given the the chain jams against the top ring when trying to shift. When I had the chain off, the cage moves to the correct outer position. I also can move the chain by hand on to the top ring and the cage is centered correctly over the top ring. I really don't think that is the problem.

    I will try tightening the right crank as tight as I can tomorrow and see if that improves anything. BTW, I did not grease or lubricate the spindle before I reinstalled the cranks because I have read to not do this. Is this true?

    Thanks,

    Jim
    Last edited by jctexas; 11-20-12 at 10:02 PM. Reason: wrong word

  6. #6
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    Quote Originally Posted by jctexas View Post
    I have sort of verified the outer limit position and the cable tension; at least to the best of my ability given the the chain jams against the top ring when trying to shift. When I had the chain off, the cage moves to the correct outer position. I also can move the chain by hand on to the top ring and the cage is centered correctly over the top ring. I really don't think that is the problem.

    I will try tightening the right crank as tight as I can tomorrow and see if that improves anything. BTW, I did not grease or lubricate the spindle before I reinstalled the cranks because I have read to not do this. Is this true?

    Thanks,

    Jim
    If the FD is only marginally short of completing the shift, it's probably a loose crank. But if it's more than 1mm or so short, I doubt your crank is that loose and something else changed.

    Tighten the crank since that can't hurt, then try adjusting the FD. If it needs any more than a minor tweak here are possibilities.

    1- you reversed an asymmetrical spindle (not likely, but not impossible, since most spindles go long side to the right. So reversing would bring the crank in, not out. But if the spindle had been in long/left and you reversed it....

    2- Wrong size balls, not likely, but smaller balls would move the spindle to the right. Most BBs use 1/4" balls, hopefully so did you. BTW - without taking it apart you could know if the balls are too small since the left cup would thread in 2-3mm farther, so take a quick look.

    As for mounting dry, that's what most makers say. However my bikes see all kinds of weather, and I've found I do best with a thin film of super light oil. This keeps water from wicking in and causing corrosion.
    FB
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    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  7. #7
    Retro Grouch onespeedbiker's Avatar
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    Quote Originally Posted by jctexas View Post
    I have sort of verified the outer limit position and the cable tension; at least to the best of my ability given the the chain jams against the top ring when trying to shift. When I had the chain off, the cage moves to the correct outer position. I also can move the chain by hand on to the top ring and the cage is centered correctly over the top ring. I really don't think that is the problem.

    I will try tightening the right crank as tight as I can tomorrow and see if that improves anything. BTW, I did not grease or lubricate the spindle before I reinstalled the cranks because I have read to not do this. Is this true?

    Thanks,

    Jim
    First you can rule out the backward spindle as, according to the tech sheet you provided, the spindle is symmetrical as you said. You shouldn't however, discount any theory, especially if it's an easy procedure. As far as checking the outside stop, you haven't verified anything by simply looking at it without watching what the chain does during shifting. If the crank is now 1mm farther out (which could be the result of a change to the bottom bracket. i.e. switching from caged bearings to loose bearings*) and that is not compensated by loosening the outside stop, the chain will probably crash into the chainring, as that is what happens just prior to the shift (Any one that has tried to slowing shift a front derailleur runs into this jamming, as the derailleur requires some momentum by the chainring for the chain to make the final jump onto the large chainring) and the effect is made worse by the Biopace chainrings I believe you bike is equipped with. Instead of rationalizing why you don't have to check the outside stop, all that is required to check it to turn the top adjustment screw 1/2 turn to the left. Remember many problems end up being something you earlier bypassed or dismissed.

    * The explanation for this is often ignored as it only seems to negatively affect bottom brackets. When you remove the retainer cage and add an extra bearing, you are increasing the size of the opening inside the bearings where the spindle goes. Because of this the spindle has to go deeper in the cup to contact the bearings. This results in the portion of the spindle that extends beyond the fixed cup will be longer; it's pretty much the same affect of using slightly smaller bearings.
    Last edited by onespeedbiker; 11-21-12 at 10:53 AM.

  8. #8
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    "I have sort of verified the outer limit position and the cable tension"
    The proper outer (high) limit setting is that which results in positive upshifting not where it looks right. After verifying the crank bolt torque (a torque wrench is very helpful here) set the limit using the "bowstring" method suggested by FB. Or better yet, start from the beginning of this procedure
    http://www.parktool.com/blog/repair-...ur-adjustments
    and follow it to the end without skipping any steps. If your chainring position has changed for whatever reason you will need to reset all of your derailleur adjustments.

  9. #9
    Senior Member Bill Kapaun's Avatar
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    Have you verified the spindle used is actually the spindle you think you have?
    There are quite a few non symmetrical spindles that have a 32MM "short" end.
    Possibly there was a replacement and someone used the short end of a spindle they had available.

    I have ran into one scenario, where the manf. had the same bike in both a double & triple version. They used the same spindle and simply flipped it as needed.
    Last edited by Bill Kapaun; 11-21-12 at 06:28 AM.

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    Thanks everyone for your suggestions. To narrow down the problem I plan on trying each one of the suggestions given and hopefully eliminate them one at a time. I will report back on my progress, probably on Friday. Have a great Thanksgiving!

    Jim

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    Can'tre Member 3alarmer's Avatar
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    I have you now, my friend..........

    Quote Originally Posted by FBinNY View Post

    As for mounting dry, that's what most makers say. However my bikes see all kinds of weather,
    and I've found I do best with a thin film of super light oil.

    This keeps water from wicking in and causing corrosion.
    I will now attempt to redirect this thread into a twenty page
    impassioned argumentathon about the "correct" procedure for
    mounting crank arms to square tapered spindles.

    Happy Thanksgiving, Francis...............
    Quote Originally Posted by Cheshire Cat
    Only a few find the way, some don't recognize it when they do - some... don't ever want to.

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