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Old 09-28-11, 10:27 AM   #1
dkrajisnik
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Sora hard to downshift

Hi all,

I have just replaced the inner wire and housing for my front derailleur. When I tried it out today, I found that it was extremely difficult to downshift from the big to the small chain ring (this is a double). It was able to downshift but it just took a lot of pressure on the thumb lever to do it. What could be the cause of this?

Bike specs:
2007 Specialized Allez Double
Sora front/Tiagra rear
Sora shifters
SRAM chain/Shimano cassette 9 speed - both replaced very recently.

I've been using Zinn, the Park Tool website and the Shimano docs on these components. I also had to adjust the high/low limit screws on this derailleur since I had set them way off to accommodate the old, frayed cable as a temporary fix. I believe I have set them up correctly.

Rear derailleur works fine. It's occasionally a bit noisy but I will get around to changing that cable/housing as well.

Interestingly, the bike seemed to be shifting properly yesterday, right after the replacement, when it was on the stand.

I've had this same problem before when the bike was nearly new. I just took it to a shop back then but I'd like to do my own maintenance now.

Thanks.

Last edited by dkrajisnik; 09-28-11 at 10:40 AM.
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Old 09-28-11, 10:47 AM   #2
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How is the tension on the front derailleur? If it is too high, both up and downshifting is a little tough. When you downshift, it'll make a loud clicking sound. Over time, this can break the shifter.

If this is not the case, then try bombing the shifter with WD40 as it could be gummed up.
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Old 09-28-11, 10:48 AM   #3
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dkrajisnik: Is the new wire seated correctly in the shifter? Did you correctly prepare the new housing, with the ends trimmed flat and with the proper ferrules correctly installed? Any frayed or loose strands inside the shifter will cause jamming. The cable must move freely since the return spring in the derailleur is what drives the shift, it pulls the cable, the cable doesn't "push" it.
Also check that the upper limit screw is not adjusted so that the cable is too tight when in the large chain ring. If it is too tight it will put the shifter under excessive tension which will make it difficult to release the shifter for downshifting. When you had the problem in the past what fixed it?

Last edited by dsbrantjr; 09-28-11 at 10:53 AM. Reason: added comment
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Old 09-28-11, 10:48 AM   #4
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+1 on cable tension.
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Old 09-28-11, 11:14 AM   #5
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The tension may well be too high. There is a very loud clunk when downshifting. I'll try playing around with this when I get back home. I just used a pair of pliers to pull the wire. Any tips on how to best set the tension? How tense should it feel in the low gear?

dsbrantjr, I cut the housing and cable to the same length as the old ones. The housing ends may not be 100% perfectly flat but they looked pretty good. I used a Park Tool cutter. Ferrules are installed. The cable is seated properly. As I said, when it happened before, I just took it to the shop. I was way too scared to even think about messing with my new bike back then.

My understanding is that when I push the thumb lever to downshift, the shifter releases some of the cable, lowering the tension. When I upshift, the shifter swallows a bit more of the cable, increasing tension. The change in tension is what causes the derailleur to move. Am I right here? Anyway, I installed the cable when the shifter was in the low gear setting, as per all of the instructions I have read. It is possible that setting the tension too high here could lead it to be WAY too high when shifted to the high gear.

Last edited by dkrajisnik; 09-28-11 at 11:58 AM.
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Old 09-28-11, 12:07 PM   #6
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Without a 3rd hand tool, I use a pair of pliers to pull the cable so there is not any slop, but without pulling too hard. I then screw the pinch bolt down a bit until the cable doesn't move. Then I check the tension by feel. If it is adequate, I'll screw the bolt down the rest of the way.

If you have a cable tension adjuster, I would unscrew it at about half way then pull the cable as tight as you can. Then screw the adjuster in to release tension. If it is a new cable, it will "stretch" over time, and then you are at a good starting point to increase tension.
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Old 09-28-11, 12:35 PM   #7
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How tense should it feel in the low gear?
It doesn't really matter. On a double, all you need to worry about tension-wise is getting the chain to the big ring.
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Old 09-28-11, 12:42 PM   #8
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Without a 3rd hand tool, I use a pair of pliers to pull the cable so there is not any slop, but without pulling too hard. I then screw the pinch bolt down a bit until the cable doesn't move. Then I check the tension by feel. If it is adequate, I'll screw the bolt down the rest of the way.

If you have a cable tension adjuster, I would unscrew it at about half way then pull the cable as tight as you can. Then screw the adjuster in to release tension. If it is a new cable, it will "stretch" over time, and then you are at a good starting point to increase tension.
That's what I did with the pliers except what do you consider adequate?

I'm a bit confused about some of the tools you mention. Is a 3rd hand tool the same things as a 4th hand tool or a cable tension adjuster. Is the Park BT-2 considered one of these?

Here are the docs on the Sora shifter: http://bike.shimano.com/media/techdo...9830615004.pdf

This is confusing. There seem to be 3 clicks on this shifter, though it is for a double. My understanding is that furthest left (on the indicator) should be the big chainring, the furthest right should be the small chainring and the middle should be used for trimming. But that PDF seems to suggest that the middle position should be used for the big ring? Or am I reading it wrong? Should it take one or two strokes to get from small to big?

Last edited by dkrajisnik; 09-28-11 at 12:53 PM.
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Old 09-28-11, 01:10 PM   #9
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Does anyone know if Sora trims? Some shifters have a soft, intermediate shift in order to eliminate chain rub on either chainring. That may be the 3rd click you feel. "Adequate" is no slop in the line without binding the derailleur (i.e. loud clunk and excessive tension).
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Old 09-28-11, 01:26 PM   #10
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Yes, Sora does trim with a double. Look at the PDF document, there are details there. My problem is most likely cable tension, I will look at it at home. But I am also confused on the proper click position for the big chainring.
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Old 09-28-11, 01:36 PM   #11
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dkrajisnik: Follow these instructions to adjust your front derailleur: http://www.parktool.com/blog/repair-...ur-adjustments Start at the beginning and do not skip any steps even though you may think they are not important. Especially heed their advice about shifting by putting tension on the shifter cable by hand instead of using the shifter. This is to separate the adjustment of the limit screws from the influence of the shifters. The key to adjusting cable tension is to have just the minimum tension required to accomplish the upshift and no more. You should only adjust the limit screws and cable barrel adjuster by 1/8th turns, or less.

As to the 3rd (or 4th) hand tools, I find them more useful for adjusting/attaching brake cables than shift cables, since there should be minimal tension on a shift cable when you are attaching it, unlike brake cables. The shifter should be in its most relaxed position, with the maximum length of cable paid out, and the derailleur against the low limit stop. The cable should then be tensioned with the barrel adjuster until the upshifts are accomplished smoothly. This is all covered in the Park instructions.
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Old 09-28-11, 03:33 PM   #12
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... I will look at it at home. ...
You are not at home? Are you using Bike Forum while you are at work?
Who would have thought of doing that?
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Old 09-28-11, 06:32 PM   #13
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Just look at the Shimano installation instructions and it should be very simple. There's really nothing confusing about it.

I've installed quite a few front derailleurs and have never had to use any tool other than the correct hex key for the pinch bolt.

First, disconnect the cable from the FD. Holding on to the loose end, shift the left shifter up and down and make sure the cable is very smooth and easy going through the housings. If you feel any hang up at all, remove the housings, make sure they're square, and that the center lumen is clear - I usually use a small nail or pick to just open them up if necessary.

Next, put everything back together and set the barrel adjuster for the front shifter/derailleur about 2-3 full turns out from fully in.

Using your hand, make sure the high and low derailleur stops are at the correct position. If they were good before and you didn't mess with them, just leave them be. You should push the FD to the stop screw over the big ring and adjust as necessary to get the correct position recommended by the Shimano installation instructions. The FD, not connected to the cable yet, should be sitting properly over the small chain ring. Adjust stop/limit screw if not. Leave it resting there.

Put the left shifter in the correct position to be on the small chain ring (fully released with the Sora's thumb shifter).

Run the cable end through where it is supposed to attach to the FD (make sure you have that right!). Tighten up the pinch bolt so it doesn't quite grab the cable, so that you can still pull it tight with one hand firmly gripping it. Use a pliers if necessary (I usually just use my hand).

Pull the cable tight with your hand, and with the other hand, tighten the pinch bolt to hold the cable well.

This should get you in the ball park. Shift the left shifter fully (two clicks?) so that the FD moves over the large ring. Does it fully seat against the stop scrrew? If not, tighten the cable tension with the barrel adjuster.

Your derailleur should work well now. Frankly, using the above steps, the only thing I've every used the barrel adjuster is to adjust the trim positions.

Last edited by Camilo; 09-28-11 at 06:36 PM.
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Old 09-28-11, 08:00 PM   #14
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How is the tension on the front derailleur? If it is too high, both up and downshifting is a little tough. When you downshift, it'll make a loud clicking sound. Over time, this can break the shifter.
Exactly. Too much cable tension pulls the cage too tight against the outer limit screw. The ratcheting action of the downshift momentarily adds more tension, which will eventually wear out the ratchet. Front derailleur cable should be tightened to the threshold of consistent upshifts and the cage clearing the chain when on the big ring. The limit screw should be set so the cage just kisses it lightly, not slamming it hard.
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Old 09-29-11, 09:48 AM   #15
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There wasn't too much tension. The cable was quite loose, not floppy, but not tense either.

I think there is a fundamental problem here. How can I possibly adjust the front derailleur if I don't know how it works? I am now thinking that it may not be a full two clicks for the big ring to engage. Rather, there should be one full click and a slight trim if necessary. Using this method, it's no longer difficult to downshift. Can someone please look at the PDF I posted a while back and confirm that this is how it's supposed to work?
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Old 09-29-11, 12:34 PM   #16
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In my experience, there is NO such thing as a "tension" adjustment when the FD is already engaged in top gear. The FD has a return spring and a cable routing design for that model of FD. It's fixed and cannot be adjusted. The small changes in cable tension are what MOVE the FD inboard and outboard to make the shift. And the small barrel adjuster on the braze-on downtube mount? That's just to adjust the slack in the cable for the start position so the brifter engages when it should. But there is NO cable tension adjustment once the FD is known to click and engage and shift.

What we need to do is to step back and ask some very simple questions:

1. Is there tremendous resistance in shifting in both directions? If yes, then look at cable run, FD geometry (e.g. do you have a different model like a top-pull FD? or a dual mode FD that requires a slightly different cable routing?), and just flex the FD in and out by hand. If you're an adult without arthritis, then it should be smooth but require some small, but firm pressure. If you're going to break a thumb bone on pivoting the FD, then something is jammed. Did you position it at the right height? At the right rotational yaw?

2. If there is only harsh resistance in shifting when downshifting to the small/resting ring, then disengage the FD cable, hold it in one hand and tug it with some tension. Now shift the brifter, first to the big ring indexed position, then back down. Change the tension with the hand holding the FD cable. Does the brifter shift when you vary the tension? If it upshifts but won't down shift with moderate hand tension easily, then you may have a defective left brifter or something is gummed up in the racheting mechanism so it's only able to upshift easily.

3. If it's working fine up to this point, look under the BB and cable routing. Make sure you don't have a groove worn in the BB that is grabbing cable and preventing free slide of the cable. And then take a very hard look at the cable routing. You may have the routing correct, but you clamped it on the wrong side of the fixing bolt. A few mm change on a 2cm lever arm can increase required tension by a LOT. So look at it again.

Just remember, there is no user serviceable cable tension once you've got the cable pre-tensioned already to pick up slack before shifting. The tension in the cable is what it is once you've already shifted.
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Old 09-29-11, 12:49 PM   #17
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There wasn't too much tension. The cable was quite loose, not floppy, but not tense either.

I think there is a fundamental problem here. How can I possibly adjust the front derailleur if I don't know how it works? I am now thinking that it may not be a full two clicks for the big ring to engage. Rather, there should be one full click and a slight trim if necessary. Using this method, it's no longer difficult to downshift. Can someone please look at the PDF I posted a while back and confirm that this is how it's supposed to work?
Sounds like you've got a triple shifter on a double chainring. You should be hitting the big ring on just one full click, and one full click to get you back down again. Loosen outer limit screw while working on this. Tighten cable until you hit the big ring in one click. Then tighten outer limit screw to lock prevent the cable from pulling the the cage into the third position. Then fine tune. There should be just a slight bit of slack in the inner (small ring) position.
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Old 09-30-11, 10:24 AM   #18
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All right, I think I have this thing figured out.

First I studied that Shimano PDF and came up with how the shifting is supposed to work on a double. To upshift, a single stroke is required to engage the big ring. An extra trim stroke may also be required but this will not click. To downshift, you must reverse the upshift. If the trim was done on the upshift, the first click will reverse the trim and the second will engage the small ring. This seems to index shifting with a friction component but I honestly think that that is how it works.

Then I adjusted the front derailleur with the following steps:
1. Mount the derailleur, checking position and rotation angle.
2. Set the L screw correctly so that inner cage plate does not rub chain on lower cogs.
3. Remove the H screw.
4. Attach the cable.
5. Adjust cable tension and test upshifts. Since the H screw is gone, that will not factor into the upshifting. I think this is better than pulling the cable with your hands but some may disagree. You must only be careful not to overshift the trim. If you do, the downshift will be difficult.
6. Replace the H screw and tighten to prevent overshifting the trim stroke.
7. Fine-tune.

The result is relatively smooth shifting on the front derailleur. With the right trim, the only combinations that generate noise are the smallest two cogs on the rear and small chainring on the front. Small-small noise happens even with the front derailleur removed and I believe that they are caused by the chain rubbing on the big chainring. This is an "illegal" combination anyway.

Thanks to all who helped. Thanks to all who helped, stay tuned for my thread on my rear derailleur woes!
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Old 09-30-11, 10:59 AM   #19
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Glad to see it worked. No need to remove the H screw (you could lose it!).
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Old 09-30-11, 12:14 PM   #20
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I removed the H screw so that it wouldn't block the upshift. This prevents mixing up cable tension issues with limit screw issues, or so I believe.
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Old 09-30-11, 06:10 PM   #21
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All right, I think I have this thing figured out.

First I studied that Shimano PDF and came up with how the shifting is supposed to work on a double. To upshift, a single stroke is required to engage the big ring. An extra trim stroke may also be required but this will not click. To downshift, you must reverse the upshift. If the trim was done on the upshift, the first click will reverse the trim and the second will engage the small ring. This seems to index shifting with a friction component but I honestly think that that is how it works....
Yes! That's how my Sora brifters work. There is a trim stroke on the bottom ring too. Otherwise the chain rubs against the FD when in higher gear (smaller outboard cogs) in the rear. But this can be bypassed by pushing harder sideways to do a full stroke inward while shifting. The equivalent full stroke on the right brifter yields a 2 cog down-shift in the rear. A single small stroke switches just one cog. I was tempted to adjust the H-screw on the FD out a little to allow more motion because I felt the trim stroke on the big chain ring was never engaging. But I don't ride with a Shimano compatible crank or FD, but something made in 1986 by Sakae and Suntour. And allowing for the trim stroke a bit more outboard motion has yielded two shifts that came off on the outside of the crank, scratching the right crank arm a little. So I adjusted the H-screw back in a little to prevent the cage from going futher out again. I don't get FD rub in top gear (big ring, small cog) so I think it's all adjusted now.
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