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Unable to adjust front derailleur, please help

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Unable to adjust front derailleur, please help

Old 07-24-21, 10:20 AM
  #1  
bicycle126312
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Unable to adjust front derailleur, please help

I have an older Cannondale Synapse road bike with a 105 groupset, the front derailleur won't shift up consistently.

It has no known issues, the cables are not noticeably worn and the shifters (front and rear) don't feel sluggish to operate.

I've:

* Aligned the derailleur vertically so that it sits about 1-2 mm above the big sprocket.

* Tightened the L screw so that it almost but not quite touches the inside of the chain.

* I've done the above while the tension bolt for the cable is loose, now with the front gear mechanism in the lowest position, and the barrel adjuster in the most slack position, I use a pair of pliers and pull firmly on the cable while I tighten the tension bolt for the front derailleur.

* I try to shift to the big sprocket, but it skips and can't quite get up. So I need to tighten the barrel adjuster to make it even be able to get up at all. I have to tighten it to the maximum position.

* I've also adjusted the H screw so that it can't shift too far and also so it doesn't rub against the inside of the chain when on the big sprocket.

My problem is that while I can get it up into the big sprocket doing this, it doesn't consistently go up. It skips and requires me to pull the shifter manually past the natural point of making an upshift.

I've tried to start over many times by now. Since it appears to help giving it some assistance by pushing it past the natural point of the upshift, I've tried to apply more force when using pliers and having the tension bolt loose, enough that I start tilting the entire bike stand. This doesn't seem to make any difference compared to just using moderate force.

I also don't understand why I need to max out the barrel adjuster (keep in mind I start with it in the most slack position) just to get it to upshift at all.






I've watched several videos on how to do this:

This one is ok:
This one goes into more details:

I still can't do it, and I'm hoping someone can point out a mistake I'm making.

Last edited by bicycle126312; 07-25-21 at 09:50 AM.
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Old 07-24-21, 01:45 PM
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Try tweaking the alignment of the cage a little. It's supposed to be parallel to the chain ring of course but that can be difficult to actually eyeball accurately. If it's just a little out of alignment so the tailing end is a little bit angled inside (toward the frame), it might affect the ability to shift to the large ring. If it does appear aligned correctly to you, still turn it a bit so the tailing end angles out just a bit more. That might solve your problem. After that, you might have to adjust your limit screws again to avoid rubbing chain on cage.

This has helped me in the past. It was either that my eyes were not serving me well in the original alignment, or that the cage simply needed to be angled out a bit to work well. I don't know which was the issue, but the solution was to angle it out more than it was when it wasn't working.
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Old 07-24-21, 01:50 PM
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Did you recently change the chain? What "speed" chain and how many cogs on the rear of your bike? Did you recently change the crankset, what "speed" crank did you get?

Did you recently change anything else? FDR maybe? You know what the next question is.


However, it might just be that you don't have the cable put into the pinch bolt the correct way, or something has gotten off with the way it's routed around the BB.
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Old 07-24-21, 08:48 PM
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There is a trick where you don’t set your L limit until after you attach the cable. I have not needed to do this, but it is used on new front derailleurs where there can be no slack.

Turn the L limit a couple(?) of turns, keep your barrel adjuster in the middle, get the cable tight as you can and then back out the L limit screw.

Others here can give you better detail. I’m not sure how much you need to move the cage.

John
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Old 07-24-21, 09:14 PM
  #5  
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How old are the actual cables and housing? Although it can happen with any shimano group my experience is that 105 is the worst at having the cable fray in the housing which shows up as lazy shifting. It also doesn't take much for a cable to develop a small kink that isn't as noticeable under tension but can still make for lazy shifting. If the chain is worn, have you checked for chain stretch? The wear can show up in side to side movement and the chain be a little too floppy to easily make the shift.
If I know I have good cables, housing and chain. Then first is to align the front der which those videos should have covered, basically outer plate parallel to the outer chainring, height (which you should avoid messing with) just a couple dimes width above the chainring. I like to pedal the bike which the rear der in 1st/lowest gear and push the front der cable down with my thumb where its heading down the downtube and pull it away from the frame so the der shifts to the large ring, then I slowly let the cable retract till the der drops the chain to the small ring. I might have to do this a couple times but it tells me where the lower limit screw is adjusted to, once I set the screw I do it a few more times quicker to mimic the shifter and make sure it drops with ease. If it continues to shift smoothly I tighten the limit screw in 1/4 turns till it isn't quite smooth and back off a 1/4 turn. Once that's set, make sure your adjustment barrels are 90% screwed down and retighten the cable at the fixing bolt. A 3rd hand cable tool helps to get the tension tight. Now with the upper limit screw backed out, shift to the large ring and tighten the limit screw till the front der just moves towards the inside. Move the rear der to your high gear, drop the chain the small ring and using your thumb again while pedaling the bike, pull down hard on the cable. The goal here is to see if the chain will overshift off the crank, if it does tighten another 1/4 turn and try several more times. Once the chain doesn't overshift, and should be easily dropping to the small ring you can adjust the cable. If you had to tighten the upper limit screw a lot to stop the chain popping up from the shift that told you where to set the upper limit screw to begin with you might need to let out a little slack with the adjustment barrel. Otherwise, just tighten it a couple turns keeping an eye that the der doesn't move off the lower limit screw from chain tension and you should be good. With a good cable, housing and chain this has never failed me for setting the adjustment.
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Old 07-25-21, 12:07 AM
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It is difficult to tell without seeing the derailleur, but it sounds like you might have inadvertently changed the cable routing around the cable pivot point, changing the leverage. I don’t know which version of 105 you have (they change from model to model), but there are typically two ways to route the cable to accommodate the different angles at which the cable comes up from the bottom bracket. If you reduce the leverage, it won’t shift up correctly.
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Old 07-25-21, 09:52 AM
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Originally Posted by bitpuddle
It is difficult to tell without seeing the derailleur, but it sounds like you might have inadvertently changed the cable routing around the cable pivot point, changing the leverage. I don’t know which version of 105 you have (they change from model to model), but there are typically two ways to route the cable to accommodate the different angles at which the cable comes up from the bottom bracket. If you reduce the leverage, it won’t shift up correctly.
I've added some pictures to the original post now. I have one of the vertical alignment of the derailleur, one of the cable, and one of the "back to front" alignment of the derailleur.

I don't think there is any way to adjust the angle of the derailleur.

Does the cable look ok?
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Old 07-25-21, 09:57 AM
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Originally Posted by Camilo
Try tweaking the alignment of the cage a little. It's supposed to be parallel to the chain ring of course but that can be difficult to actually eyeball accurately. If it's just a little out of alignment so the tailing end is a little bit angled inside (toward the frame), it might affect the ability to shift to the large ring. If it does appear aligned correctly to you, still turn it a bit so the tailing end angles out just a bit more. That might solve your problem. After that, you might have to adjust your limit screws again to avoid rubbing chain on cage.

This has helped me in the past. It was either that my eyes were not serving me well in the original alignment, or that the cage simply needed to be angled out a bit to work well. I don't know which was the issue, but the solution was to angle it out more than it was when it wasn't working.
I looked for ways to tweak the alignment of the cage in relation to the line the chain forms, but I don't think it has this feature?

Can you see any in the pictures I've added? I included a few pictures in the middle of the original post.
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Old 07-25-21, 10:00 AM
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Looking at it... my guess is that cable is on the wrong side of the pinch bolt.
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Old 07-25-21, 10:00 AM
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Originally Posted by Russ Roth
How old are the actual cables and housing? Although it can happen with any shimano group my experience is that 105 is the worst at having the cable fray in the housing which shows up as lazy shifting. It also doesn't take much for a cable to develop a small kink that isn't as noticeable under tension but can still make for lazy shifting. If the chain is worn, have you checked for chain stretch? The wear can show up in side to side movement and the chain be a little too floppy to easily make the shift.
If I know I have good cables, housing and chain. Then first is to align the front der which those videos should have covered, basically outer plate parallel to the outer chainring, height (which you should avoid messing with) just a couple dimes width above the chainring. I like to pedal the bike which the rear der in 1st/lowest gear and push the front der cable down with my thumb where its heading down the downtube and pull it away from the frame so the der shifts to the large ring, then I slowly let the cable retract till the der drops the chain to the small ring. I might have to do this a couple times but it tells me where the lower limit screw is adjusted to, once I set the screw I do it a few more times quicker to mimic the shifter and make sure it drops with ease. If it continues to shift smoothly I tighten the limit screw in 1/4 turns till it isn't quite smooth and back off a 1/4 turn. Once that's set, make sure your adjustment barrels are 90% screwed down and retighten the cable at the fixing bolt. A 3rd hand cable tool helps to get the tension tight. Now with the upper limit screw backed out, shift to the large ring and tighten the limit screw till the front der just moves towards the inside. Move the rear der to your high gear, drop the chain the small ring and using your thumb again while pedaling the bike, pull down hard on the cable. The goal here is to see if the chain will overshift off the crank, if it does tighten another 1/4 turn and try several more times. Once the chain doesn't overshift, and should be easily dropping to the small ring you can adjust the cable. If you had to tighten the upper limit screw a lot to stop the chain popping up from the shift that told you where to set the upper limit screw to begin with you might need to let out a little slack with the adjustment barrel. Otherwise, just tighten it a couple turns keeping an eye that the der doesn't move off the lower limit screw from chain tension and you should be good. With a good cable, housing and chain this has never failed me for setting the adjustment.
I'm unfortunately unable to tell you how old the cables are, as I bought this bike second hand.

However, the chain and cassette in the rear, are both new.

But you're thinking that wear in the cables can make for inconsistent shifting?

Thank you for describing the procedure in detail, I believe I'm already doing something similar to it, the second video in my original post describes something quite similar. But good to confirm.
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Old 07-25-21, 10:08 AM
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The FD braze on is a slot slightly bigger than the screw diameter. you can rotate the FD with the same vertical position to attain some alignment.
I try to follow recommendations but when they fail, I resort to giving myself as much adjustment range as possible, much like @70sSanO suggests.
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Old 07-25-21, 10:41 AM
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I agree with the mis-routed cable at the pinch bolt theory. T'were it around the back instead of straight up the front, the pull leverage would be increased a fair bit. I'm also suspicious about where the compression on the cable closer to the end came from. But I'd try wrapping the cable around the back of the punch bolt first.
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Old 07-25-21, 10:45 AM
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Originally Posted by trailangel
Looking at it... my guess is that cable is on the wrong side of the pinch bolt.
I think we have a Bingo ovah heah
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Old 07-25-21, 12:08 PM
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I tried flipping it around the other way on the pinch bolt, however, this was clearly not the correct way to do it. It probably doesn't show that well in the pictures, but when it is flipped around the other way, it only pulls the cage down, not to the side. Hence with that arrangement, it is not possible to move the cage at all with the shifter.

However, it seem to have found the problem.

The problem appears to be that my bike just had installed mudguards, and the mudguard on the rear wheel prevents full movement of the derailleur. I didn't notice this at first, but it pushes against the plastic and deforms the mudguard slightly, but this also somewhat limits its movement. After cutting out a piece of the plastic to allow it full movement, it works much better, although not perfectly.

Thanks for all the help guys.
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Old 07-25-21, 12:29 PM
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Originally Posted by trailangel
Looking at it... my guess is that cable is on the wrong side of the pinch bolt.
Yep
No harm in trying it.
Start over with the cable on the inside.
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