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Old 05-09-11, 08:31 AM   #1
bluefoxicy
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Correct derailleur tension seems to be "very loose"?

I took the slack out of my front derailleur cable in low. ... this was a bad idea. The cable was configured such that it had ... well, quite a bit of play. There wasn't actually any tension in the wire, at all. In fact, there was a LOT of extra slack: I took up an inch and a half easily.

Bad idea.

I wound up putting most of that slack back to get it to shift correctly. There's also two screws on my derailleur that appear to be unmarked limit screws, but the docs tell me about these:

http://techdocs.shimano.com/media/te...9830684418.PDF

I guess I need to run through all this to get indexing and shifting right; but why so much slack? Is that just because my derailleur is horribly adjusted and I need to fix it? What am I missing here, besides any skill or experience or any clue about what I'm doing?
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Old 05-09-11, 12:09 PM   #2
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The front derailler cable will usually be completely slack in the lowest gear. You can think of it this way, the lower stop sets the first gear, the cable tension sets the middle and the upper stop sets the third.

An inch and a half is a ridiculous amount of slack though, I haven't ever seen a shifter that can take up that much cable. Is it shifting into the next ring ok?
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Old 05-09-11, 02:46 PM   #3
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Yeah, it shifts to the next ring okay. That's what confuses me. I just found this pile of ridiculous dangling cable and went, "Hmm! I should tighten this up!" and it turned out to be a really bad idea.
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Old 05-09-11, 05:44 PM   #4
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Awesome. I fixed the upper limit, tension ... messed it up at first, then I figured out how the indexer worked and fixed that center shift (seriously, I had it shifting perfectly to low, and then jumping directly to high, skipping middle). There are still some odd issues: it rattles in Low/1 but not in Low/2; a little drag up in High (less now); etc. I need to make adjustments.

The bike is faster now, though. The amount of drag the chain had with the cage originally was significant and, despite still being wrong, it's in so much better tune now that I can accelerate a bit faster. I'd blame my body's dire need for rest yesterday and subsequent recovery from a week of commuting; but I tuned it before leaving work today, so I have a morning and afternoon sample. But I am getting faster

I really need to check out both derailleurs I guess. And these cables; I set up the brakes and they became too soft, so I rolled out the barrel and they ... became too soft again after a couple minutes? Cable doesn't seem to be slipping off the brake itself.
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Old 05-09-11, 05:49 PM   #5
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Originally Posted by bluefoxicy View Post
The amount of drag the chain had with the cage originally was significant
So you were riding around with the chain dragging against the FD cage? That's a pretty good sign something is wrong. If you didn't wear out your cage too badly consider yourself lucky. That's a great way to ruin one.
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Old 05-09-11, 07:34 PM   #6
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I've never had a derailleur work correctly with slack in the cable.
Are your shifters and derailleurs the same brand?
Follow the setup instructions found at www.parktool.com. Do all of the steps in proper sequence leaving nothing out.

Last edited by Al1943; 05-09-11 at 07:37 PM.
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Old 05-09-11, 07:49 PM   #7
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Sorry, but I can't buy you having taken up 1-1/2" of slack. At that rate, it would never tighten enough to make the upshifts. True, the cable is the most slack in the smallest front ring, but that much slack is riduculous. Your previous posts about your FD don't mention that much slack or that being an issue.

Not saying you don't have cable tension issues, but if it had 1-1/2" of slack, it would have been banging against the frame and awfully annoying, if not injurious to the paint.
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Old 05-09-11, 08:35 PM   #8
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If the shifter was not in its lowest position when the cable was attached, there will be a lot of slack when shifted to the lowest position.
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Old 05-10-11, 11:17 AM   #9
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So you were riding around with the chain dragging against the FD cage? That's a pretty good sign something is wrong. If you didn't wear out your cage too badly consider yourself lucky. That's a great way to ruin one.
Yeah only in the top gear. Rattle rattle rattle. My derailleur was just barely away from the top ring, and pressed somewhat against the chain. I almost never use the top gear though... well, I'm learning. I use it now....

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I've never had a derailleur work correctly with slack in the cable.
Are your shifters and derailleurs the same brand?
All Shimano.

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Not saying you don't have cable tension issues, but if it had 1-1/2" of slack, it would have been banging against the frame and awfully annoying, if not injurious to the paint.
In my lowest gear, the derailleur is tensioned against the frame.



That part that's touching the frame moves away when I'm on the middle chain ring. On the lowest, it comes down and hits the frame. It stays there, firmly.
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Old 05-10-11, 03:09 PM   #10
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It would have helped more if the chain was on the smallest chainring and largest cog when that picture was taken. That is the combination to be in when adjusting the low limit screw.
We can't tell what is going on with the chain off.

Last edited by Al1943; 05-10-11 at 03:12 PM.
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Old 05-11-11, 09:30 AM   #11
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I'm betting that your low limit is too low. Go back to the Park Tools site and do all the steps again to see if it improves.
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