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Reconnecting shift cable to front derailleur

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Reconnecting shift cable to front derailleur

Old 01-18-11, 12:01 AM
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Reconnecting shift cable to front derailleur

Bought a slightly used bike. FD would not shift onto the smallest ring, and chain was touching FD when middle front/smallish rear. I watched few youtube clips that all followed the same theme. I then made my attempt. While trying to reattach the shifter cable, I can't get it right. Either it is too slack or too stiff to shift onto the large ring. I've taken it off and reinstalled it so many times that the cable is starting to fray. I'm frustrated. Any helpful advice? Shimano Sora, by the way.

Thanks!
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Old 01-18-11, 12:06 AM
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Have you looked at the limit screws as well?

You would probably benefit from putting some kind of barrel adjusters between the shifter and derailer. That way the cable adjustment can be tweaked without reattaching the cable.
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Old 01-18-11, 02:36 AM
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Front derailleur adjustment is one of the trickiest things to do on a bike... the following assumes the derailleur is mounted in the correct position (inner plate parallel to rings, outer plate clearing big ring by 1-2mm).

First ensure the inner limit screw is properly set, by seeing if the derailleur rubs on the chain when in smallest ring/biggest cog. If there's a gap, turn the screw until it's as small as you can get it without chain rub (remember to allow a mm or so for some flex that will occur when you're on the bike).

Then secure the cable and shift into biggest ring/smallest cog and adjust the outer limit screw in the same way, ensuring the shifter is holding the derailleur against the limit screw.

Back off any barrel adjusters on the cable to a couple of turns from fully loose, pull the cable tight while the derailleur's resting against the inner limit screw, and finally tighten the clamp bolt.

Test shifting and tweak your barrel adjuster to minimise chain rub.
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Old 01-18-11, 07:56 AM
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Originally Posted by Kimmo
Front derailleur adjustment is one of the trickiest things to do on a bike... the following assumes the derailleur is mounted in the correct position (inner plate parallel to rings, outer plate clearing big ring by 1-2mm).
Did this. I checked the outer clearance and it's roughly 2mm


Originally Posted by Kimmo
First ensure the inner limit screw is properly set, by seeing if the derailleur rubs on the chain when in smallest ring/biggest cog. If there's a gap, turn the screw until it's as small as you can get it without chain rub (remember to allow a mm or so for some flex that will occur when you're on the bike).
So far, so good

Originally Posted by Kimmo
Then secure the cable and shift into biggest ring/smallest cog and adjust the outer limit screw in the same way, ensuring the shifter is holding the derailleur against the limit screw.
It's that "secure the cable" that everyone glosses over just like this but that I am not getting right.

Originally Posted by Kimmo
Back off any barrel adjusters on the cable to a couple of turns from fully loose, pull the cable tight while the derailleur's resting against the inner limit screw, and finally tighten the clamp bolt.
This is most likely the problem, and I think that it's because I don't understand the mechanics of the cables. I was tightening the barrel until it stopped then loosening two clicks before trying to tighten the clamp. So for your way, backing off the barrel adjuster makes the cable slack, then I pull it by hand and then tighten the bolt? But then I've pulled the slack out of the cable and I'm at a position on the barrel where I can only tighten it and add more tension to a cable already under tension. Is this correct?

I really appreciate the help. I'll search to see if I can learn more about operation of cables.
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Old 01-18-11, 09:17 AM
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One more thing, is this a Shimano fd? If so, attaching the cable to the fixing bolt the right way is essential. Look at the bolt and you will see a small tab to its left. The cable must route OUTSIDE of this tab and then over the top of the fixing bolt.

If you route the cable between the tab and the bolt, the actuation ratio changes enough that the shifting will not index properly.
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Old 01-18-11, 10:05 AM
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Originally Posted by rojeho
....This is most likely the problem, and I think that it's because I don't understand the mechanics of the cables. I was tightening the barrel until it stopped then loosening two clicks before trying to tighten the clamp. So for your way, backing off the barrel adjuster makes the cable slack, then I pull it by hand and then tighten the bolt? But then I've pulled the slack out of the cable and I'm at a position on the barrel where I can only tighten it and add more tension to a cable already under tension. Is this correct?
That's an excellent description of what you want to do. The idea is to get the cable as tight as you RESONABLY can by hand and then trim the final initial tension using the barrel adjuster so that it just barely sits against the limit screw. Then check the shifting and adjust either way as required to bet smooth shifting. You MAY, by some small miracle, need to shorten the cable slightly but 99.9% of the time you'll need more tension. Hence the advice to shorten the adjuster fully until tight and then lengthen it a couple of turns for the initial setting.
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Old 01-18-11, 10:42 AM
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Go to www.parktool.com and find the instructions for setting up and adjusting the derailleur. Do all of the steps in proper sequence leaving nothing out.
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Old 01-18-11, 11:54 AM
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I find it helps to pull on the cable with pliers while attaching it in order to remove most of the slack.
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Old 01-18-11, 04:20 PM
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The shifter needs to be in its lowest position before attaching the cable.
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Old 01-18-11, 05:22 PM
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Originally Posted by relyt
I find it helps to pull on the cable with pliers while attaching it in order to remove most of the slack.
Me too, especially to do it the neat way:

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Old 01-18-11, 05:25 PM
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Originally Posted by BCRider
Hence the advice to shorten the adjuster fully until tight and then lengthen it a couple of turns for the initial setting.
I think this is the part that I am not visualizing correctly. To me, "shorten the adjuster fully until tight" means to tighten the barrel leading to a higher tension, but I think this is opposite of what you are wanting me to do.

If I make the cable shorter, am I making it more slack or more tense?

When I turn the barrel counterclockwise, what am I doing to the tension? What about clockwise turning?

Thank you!
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Old 01-18-11, 06:07 PM
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Look at your right hand. If you make a thumbs-up shape, the direction you turn any right-hand threaded fastener to go in the direction your thumb points is the way your fingers curl. Hence 'righty-tighty, lefty-loosey' when looking down on the fastener. But don't think in terms of tight and loose here, cause that's confusing. Screw in or unscrew.

So if you screw in an adjuster, it makes the effective housing length shorter, loosening the cable. Unscrewing the fastener lengthens the effective housing length, tightening the cable.

Shortening the adjuster until tight means to screw it in until it stops.
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Old 01-19-11, 01:24 PM
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Get a barrel adjuster for the front derailleur. Get a new cable, install until the cable is just under tension, don't over-tension the cable. Adjust your barrel accordingly.
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