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Old 01-04-06, 10:03 PM   #1
iamtim
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Front Derailleur Question...

Ok, recently I installed a new front derailleur on my Trek 1000 -- it's a Tiagra, to replace the 2203. It seems to be heads and tails above the 2203, but I have an adjustment question.

It (the derailleur) was riding just a little too low on the seat-tube, as when I rode in the middle chainring and applied pressure to the left crank the outside of the derailleur would rub against the teeth on the big chainring. So I moved it up just a hair, shifting into the big chainring is a challenge. If I make a concerted effort to "slam" the brifter (i.e. shift as hard and as far as it can go) it brings the chain into gear, but unless I do that the chain won't move up to the big chainring -- it's as if the derailleur doesn't move out far enough, like it's just a hair too far to the left.

I know there are two screws on the derailleur, but I'm not quite sure how they work. Which one do I turn for the minute adjustment I think I need to make? Can I adjust it out towards the big chainring further without affecting the inside (i.e. small chainring) settings? Is that what I need to do after all, or am I off in left field somewhere?

Any help is appreciated.
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Old 01-04-06, 10:16 PM   #2
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Look at cable tension first.www.sheldonbrown.com
Also mine the forums there are dozens of post about this
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Old 01-04-06, 11:47 PM   #3
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You know, for what it's worth, www.sheldonbrown.com (at least the "techie" articles) makes my eyes glaze over. I think it's because it's so one-way -- no interaction, no way to ask questions like there is here.

I'll search the forums, though.
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Old 01-05-06, 12:09 AM   #4
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Check to see if the alignment rotationally on the seat tube is correct. There are 2 methods for alignment. If you try the campy method the Shimano FD might be out of line just enough to cause problems with the big chain ring. Look at Zinn's book or any of the other resources such as Bicycling Maint book, or a Barnett's manual for the correct method. Does the derailluer have any evidence of a crash or indication that it may have been bent? The Shimano derailluer should give you great shifting if you align it correctly.
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Old 01-05-06, 12:18 AM   #5
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Quote:
Originally Posted by Deanster04
Does the derailluer have any evidence of a crash or indication that it may have been bent?
No, it's brand new. I had it installed right after my accident a few weeks back. It was shifting great -- exactly as it should -- until I moved it up the seat tube a tiny bit to alleviate the rubbing on the big chainring when I was pedalling in the medium chainring.

It appears to me to be rotationally aligned properly. I made sure I moved it on the up-down axis only, and it's in the same place rotationally as it was before the move. It just seems to me that since I moved it up it's not pushing out enough.

*shrug*
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Old 01-05-06, 12:35 AM   #6
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That's correct. The higher the FD is above the chainring, the more outwards it has to move in order to bend the chain to the same angle. So, most likely, you'll need to move it out an additional 2-3mm for the same shift. To do this, you need to undo the outer limit screw and tighten the cable a bit.

Also the cage rotation IS very important. For optimum shifting, it should NOT be parallel to the chainring, but parallel to the chain when shifted into the biggest gear combo (big-ring, smallest cog in back).

Good procedure with photos at the Park Tool site: Front Derailleur Adjustments
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Old 01-05-06, 09:18 AM   #7
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Quote:
Originally Posted by iamtim
No, it's brand new. I had it installed right after my accident a few weeks back. It was shifting great -- exactly as it should -- until I moved it up the seat tube a tiny bit to alleviate the rubbing on the big chainring when I was pedalling in the medium chainring.

It appears to me to be rotationally aligned properly. I made sure I moved it on the up-down axis only, and it's in the same place rotationally as it was before the move. It just seems to me that since I moved it up it's not pushing out enough.

*shrug*
What happened to the Shimano installation and adjustment instructions that are packed with all their products? Get the instructions from whomever installed the part. I never throw away technical literature such as this. In those instructions it will point out that the FD height and angle adjustment is always set with reference to the outermost (biggest) chainring. It is usually the first adjustment made to the FD after installation and prior to connecting the FD cable. The second and third adjustments are the outer and inner limit screw adjustments. These are very simple and should be done without the FD cable connected.

There is a chance that your BB installation quality be checked. But I'd go through the FD adjustments first. Since you said it only has the problem as you mash down on the left pedal, the force on the right side of the BB would be to push up on that side of the axle. If there were the slightest movement allowed, the effect would be to move the top of the chainring towards the center of the bike.
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Old 01-05-06, 10:52 AM   #8
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My recommendation is to go to the Park Tool website and follow All of their directions starting at the very beginning with the position of the derailleur on the seat tube. Every adjustment that you make to a front derailleur affects all of the subsequent adjustments so it's important to do all of the steps in the recommended sequence.
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Old 01-05-06, 11:24 AM   #9
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See the attached pic for proper derailleur height.

Then go to www.parktool.com to learn the rest. It shouldn't make your eyes glaze over. With that said, sometimes front derailleurs can be a PITA. The last time i upgraded my crankset it made it impossible to get my derailleur to work properly.

Despite following all the advice here and at Parktool, it still wouldn't work right. One problem was that my derailleur wasn't spec'd for the new chainwheels i had on. EVen though most here said that shouldn't matter.

I finally gave up and took it to LBS. The guy there said he spent a long time on it and had to bend the crap out of the cage to get it to work right. It has shifted flawlessly in the last 3 months.


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Old 01-05-06, 11:24 AM   #10
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Quote:
Originally Posted by Retro Grouch
My recommendation is to go to the Park Tool website and follow All of their directions starting at the very beginning with the position of the derailleur on the seat tube. Every adjustment that you make to a front derailleur affects all of the subsequent adjustments so it's important to do all of the steps in the recommended sequence.
Amen to that. When I first tried adjusting a FD I was making random changes in no particular order and was chasing my tail. After printing out the Park Tools Instructions, having them at my elbow and making myself do it from step 1, in order, even if I 'Thought' I knew better, all I can say is that I had a perfectly adjusted FD in a matter of a few minutes.

Steve W
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Old 01-05-06, 01:07 PM   #11
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One possibility is that you did not have all of the cable out of the shifter at the time you attached the cable to the derailleur. With the cable detached, flip the small shift lever several times while pulling the free end of the cable. Then re-attach and adjust.

Al
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Old 01-07-06, 06:20 PM   #12
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Hey, thanks for all your help, everyone.

For what it's worth, a buddy of mine got me an Amazon gift certificate for Christmas. With said gift certificate, I purchased "The BICYCLING guide to complete bicycle maintenance & repair for road & mountain bikes". I just got it yesterday, sat down with the front derailleur instructions, took mine off, and put it on from scratch. Now it seems to work smooth and flawlessly.

Again, thanks!
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