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Old 07-11-07, 08:21 PM   #1
stokessd
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Derailleur cables stretching?

This may belong in the mechanics section:

We have a flakey front derailleur on our Cannondale tandem. It's an Ultegra triple model. I've adjusted my share of front deraileurs over the years, and this one is a bit tricky. I have carefully dialed in the height, and angle. When I get the cable tension right to shift up and down well, I get rubbing in the smallest couple rear cogs in the largest chainring. If I tension the cable enough that I don't get rubbing in the tallest gears, then it doesn't want to shift downward.

I'm thinking that I've got cable stretch. I marked the cable and measured it with a ruler, and there is some stretch. The rear doesn't have as much tension on it and seems to work quite well.

My other possibility is the spacing on the Truvative chainrings could be slightly wider than standard. The truvative cranks haven't inspired much confidence in me. The timing chainrings are not concentric and there isn't enough play in the chainring mounting to make them so. The drive chainrings wobble a bit and aren't concentric either.

Have you tandem guys have issues with cable stretch making the front derailleur adjustment tricky? I would much rather have the left brifter be a friction adjustment, indexed front derailleur shifting is just plain dumb (IMHO).

What cables do you guys suggest?

Sheldon

Last edited by stokessd; 07-11-07 at 08:30 PM.
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Old 07-11-07, 09:35 PM   #2
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Unless your cables have a lot of wear and tear, I don't think they're the root cause of your issues. If they are a bit long in the tooth (two seasons or more), then it wouldn't hurt to replace them... as well as the housing.

Moving on the the derailleur, let me suggest you start over and follow Shimano's step-by-step tech procedure for positioning and adjusting your Ultegra FD: http://techdocs.shimano.com/media/te...9830616213.pdf

If after attempting to get them dialed in using Shimano's instructions it is still giving you trouble, we can take another look at it.

If you really don't like the way the STI levers work don't struggle with them: just get a bar-end shifter for the front and be done with it. You can leave the STI lever as it is for the brake.
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Old 07-11-07, 11:47 PM   #3
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It ain't cable stretch. Two things you have to watch out for with Shimano front derailleurs.

1. Shimano road and mountain front derailleurs are not interchangeable. You have to use the road levers with the road fd, and the flat levers with the mtb fd. However, I am assuming you kept the Cdale stock and didn't swap out the Ultegra STI levers.

2. The way you attach the cable to the fd is very, very, very, very (did I say very?) important! You DO NOT attach the cable at the side of the anchor washer (like on Campag). You run the cable outside the anchor washer (there may be a flange that you run the cable OUTSIDE of) and you anchor the cable at the top of the anchor bolt. If you do not do this, the shifter will work exactly as you have described.

- L.
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Old 07-12-07, 04:51 AM   #4
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+1 for TGs comment. Unless you have broken some cable strands at the pinch point, even if your cable is stretched, retentioning and readjustment should bring it back into line. Even with proper setup, the cable tension on the front STI der. must be dead bang on and this is accomplished by the barrel tension device near the brifter. If that little (plastic) device is worn or cranky, or the threads loose, then you will have constant troubles.

I ditched my front brifter a couple weeks ago in favor of a DA bar end friction shifter and all my troubles with front derailleur shifting went away. Front shifts are crisp and positive even under moderate loads, and I can now tune the front der. position to where it needs to be, when it needs to be there. Ahhhhh, relief.
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Old 07-12-07, 06:47 AM   #5
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I'll go back over my setup again. My adjustment is pretty close to what Shimano says in the tech note (thanks for the link TG). Based on the adjustment, of 0-0.5mm of chain clearance at the end cogs on the cassette, I am guaranteed of the chain rubbing the front derailleur. Especially given that the craptastic Truvativ chainrings don't run true.

The LBS tech (with 20 years of experience, for what that's worth) told me: "You have to shift down twice to go from the large chainring to the middle" The first click just rubs and doesn't disengage, and then another click and it jumps down. He said this with a straight face, like it was the way it was. I thought to myself that he's not got the thing adjusted correctly, and I set out to try to make it work well. So far, I'm having issues. I've got my wife's 105 and RSX shifters working well on her Symmetry, I've got her XT levers and drivetrain working well on her Terry Classic. I don't own an indexing front derailleur setup on any of my bikes, but needless to say, this is not my first time with these things.

Thanks for all the suggestions, I'll keep battling it. I'm going to measure chainring spacing on my wife’s ultegra and 105 cranks and compare it to the truvative. If the truvative chainrings are spaced slightly farther apart, that would cause the same behavior. The rings on both the timing chain and drive side don't run true, so I can believe that they are off in the other direction as well.

This is my first new bike purchase since the late 90's, and I have to say the quality of the parts has dropped considerably since the 80's. The C'dale frame braze-ons force me into some sort of bar mounted shifters, and they also force me into some sort of inline cable adjustment rather than the downtube mounted adjusters. My kingdom for a tandem Campy Super record drivetrain from the 80's (what I still ride).

lhbernhardt- thanks for the suggestion on cable mounting, but this derailleur really only has one way to mount the cable, I'm pretty sure it's the correct way, but I'll check again to make sure.

Sheldon

Last edited by stokessd; 07-12-07 at 06:58 AM.
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Old 07-12-07, 06:09 PM   #6
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Cranks & FD alignment: Unless your cranks are positioned too far outboard (might want to verify that the chainline is correct: Truvative spec's 46.5mm), I would think you or your LBS wrench should be able to get the front derailleur set to eliminate routine chain rub when you are running the chain in the big ring and small cog under most conditions. I say most conditions only because tandems do have a tendency to make cranks and chainrings deflect under big pedalling loads so if you're really grinding out a lot of power in your biggest gear it's not all that uncommon to hear some chain rubbing... at least that's been my experience. Of course, all of our road tandems have had 110mm BCD cranks running 53t or 54t rings which are more succeptible to deflection than the 130mm BCD cranks. However, I will admit to having removed some material from the front derailleur stops on one of our tandems to accommodate an unusual mix of cranks and chainrings that placed the big chainring out at the limit of my Campy Racing-T FD. Anyway, there's a solution out there but without seeing or being able to put hands on your bike this is one of those things that's a bit hard to trouble shoot via the net.

Shifters:

Quote:
Originally Posted by stokessd
The LBS tech (with 20 years of experience, for what that's worth) told me: "You have to shift down twice to go from the large chainring to the middle" The first click just rubs and doesn't disengage, and then another click and it jumps down. He said this with a straight face, like it was the way it was.
Lets move onto Shimano Technical Cut Sheet Part II: Note the description of the inner (b) lever operation and the reference to the Front Derailleur's trim adjustment in the snapshot below or at the .pdf file found at this link: http://techdocs.shimano.com/media/te...9830616322.pdf

I don't use Shimano so perhaps others with the same C'dale RT or at least current Ultegra triple levers can comment on how their shifters work relative to what the cut sheets suggest. The last bikes I've fiddled with that had Ultegra were old enough to not have the additional index positions that I believe have been added in more recent years. Therefore, if I understand what I've read, it would seem that your LBS wrench isn't shining you on.
Attached Images
File Type: jpg trim.jpg (47.9 KB, 12 views)

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Old 07-13-07, 10:31 AM   #7
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No, you don't have to shift down twice to get the middle ring. I've been riding STI 9-speed Ultegra triples since 1999 and have the same on our new used Co-Mo. It works perfectly. Sounds like too much cable tension to me. Coming down from the big ring, the first click should drop you into the middle ring, and the smallest 7 cogs should be reachable without rubbing. The second click trims the FD in a hair and allows you to reach the inner two rear cogs without rubbing. The third click gets you the granny ring. Upshifting, a full shift gets you the outer of the two middle ring positions and another full shift gets you the big ring.

You can also use the inner of the two middle ring positions to allow you to access the smaller cogs from the granny ring, but that's not a good idea because it puts more tension on the chain, increasing wear. Better to shift into the middle ring. All this works as above on our Co-Mo. It's a bit dependent on drive train geometry. On my single Trek, all the rear cogs are reachable without rubbing from the outer of the two middle ring positions, but not so on the Co-Mo.

The granny/big cog combination should just barely not rub. Same with the big ring/small cog combination. You have to get the starting cable tension just right, with the FD shifter shifted all the way down. Also make absolutely sure that the shift cable end isn't hanging up inside the shifter. That happens sometimes and can drive you nuts. Pull back on the brake lever with the QR released and watch the cable end while you shift up and down as someone else spins the pedals.

I've got Race Race rings on the Co-Mo and Ultegra rings on the Trek. And all that said, I've never worked with 10-speed triples. They may be different. And as others have said, cable stretch makes absolutely no difference, other than that one must readjust as the cable stretches, as all cables do. Usually the little thumbscrew on the down tube gives enough adjustment for that.

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Old 07-13-07, 12:57 PM   #8
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As we have stated in previous posts, we originally spec'd D/A brifters on our Zona tandem. Rear worked just fine, front was problematic . . . fought front D/A der. for 3,000 miles. Stoker Kay finally said 'go back to barcons, they have always worked just great.'
Followed stoker's advice, went to D/A 9 speed barcons front and rear. We're happy (!) with over 12,000 miles on the barcon setup.
Hi-tech is not always the best; lo-tech works just fine for us!
Pedal on TWOgether!
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Old 07-13-07, 02:59 PM   #9
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Quote:
Originally Posted by zonatandem
Rear worked just fine, front was problematic . . . fought front D/A der. for 3,000 miles. Stoker Kay finally said 'go back to barcons, they have always worked just great.'
You should have tried Campy's Ergos before giving up on integrated shifting...

While our total tandem miles pale in comparison to yours and many other teams, we have over 50k tandem miles on Ergo's since '98 and never any problems: just a right lever shift disc & spring replacement at around every 10k - 12k miles keeps them working just fine.

I can't think of any reason including cost that I'd go back to down tube or bar-end shifters have been spoiled rotten by Ergo.

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Old 07-13-07, 03:51 PM   #10
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Have used Campy Ergo and find their shifting a bit more intuitive than STI. 50K+ miles on Ergo is a fine testimonial!
Have put mega-miles on barcons without any issues and never had to replace anything except a few cables.
I thought SRAM would've taken a bite out of the market by now.
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Old 07-13-07, 07:46 PM   #11
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I've spent some more time with the derailleur. I've also measured the frame. I'm not sure the exact chainline distance, but my seat-tube to chainstay angle is more like 61 deg rather than the recommended 63 deg. I've been over and over the alignment procedures and I think I've got everything correct.

The long and short of my problem is that the front derailleur doesn't seem to have enough travel. So I can skew the travel to the outside and keep the large chainring small frehub cog combo from rubbing, but then I can't reliably downshift to smaller chainrings. If I skew to the inside, I can downshift and upshift reasonably well, but the large chainring small rear cog combos rub (like the smallest three rear cogs). I've been over the derailleur positioning, cable mounting, and outer cables, frame braze ons (weld ons).

My suspicions:

- The truvativ chainrings are spaced slightly too far apart
- the cable stretches slightly as the tension increases

Regardless, I've got to find a solution to this. It is looking more and more like I'm tossing these silly brifters in the trash and going with bar-ends. I'd like to go with downtube shifters but c'dale made that impossible.

Are the campy brifters and derailleurs better? They used to be worlds better than shimano in the pre indexing days. How are they these days?

Sheldon
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Old 07-13-07, 08:10 PM   #12
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Two major differences:

1. 9 speed triple left-hand / front derailleur shifter has 9 index positions which essentially replicates indexed bar-end or downtube shifter trim positions.
2. Completely different interface with the hand and fingers relative to grip and shifting. Having small hands, I found the Ergo's to be a much better fit.

With the introduction of the Shimagnolo (since discontinued) and J-Tek shiftmates, you can now use Campy's Ergo levers with Shimano deraileurs and cassettes, so a complete hardware change isn't required to make the change anymore so that making the switch to bar-ends. Of course, the conversion cost isn't insignificant. The only thing about the J-Tek is that you do need to occassionally re-set the pulley to it's 1:00pm clock position to keep shifting as good as it can be.

This article is a bit dated, noting that both Campy & Shimano have continued to make improvements and refinements in their shifters. However, many of the major differences associated with the "fit" of the different shifters still applies: http://www.thetandemlink.com/stivsergo.html

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Old 07-13-07, 08:29 PM   #13
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Quote:
Originally Posted by stokessd
My suspicions:

- The truvativ chainrings are spaced slightly too far apart
- the cable stretches slightly as the tension increases
Interesting that you're the only one that has this problem. I never had this problem with my Cannondale and the original Shimano levers. However, I switched to Campy with Jtek because my brain found it too hard to switch between my single bikes with Campy and the tandem
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Old 07-13-07, 08:56 PM   #14
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Quote:
Originally Posted by rmac
Interesting that you're the only one that has this problem. I never had this problem with my Cannondale and the original Shimano levers. However, I switched to Campy with Jtek because my brain found it too hard to switch between my single bikes with Campy and the tandem

The fact that I'm the only one with the problem is making me feel like a moron.

I've also got a timing chain which will not stay quiet. I paraffined the chains and the drive chain is quiet as a church mouse, and the timing chain started squeaking after about 20 miles. I re-paraffined it and it did it again after another 20. I switched to white lightning and each time the chain is good for about 20 miles. The rollers on the chain are not smooth and polished, but are are scared and gouged up. I'm wondering about the inside of the links and if I've got a defective link. I really don't want to go to a wet lube. I'm going to toss that chain (with it's visible issues).

I'm also going to pick up a new front derailleur cable and see if that fixes the problem.

Sheldon
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Old 07-13-07, 09:25 PM   #15
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Quote:
Originally Posted by Carbonfiberboy
No, you don't have to shift down twice to get the middle ring. I've been riding STI 9-speed Ultegra triples since 1999 and have the same on our new used Co-Mo. It works perfectly. Sounds like too much cable tension to me. Coming down from the big ring, the first click should drop you into the middle ring, and the smallest 7 cogs should be reachable without rubbing. The second click trims the FD in a hair and allows you to reach the inner two rear cogs without rubbing. The third click gets you the granny ring. Upshifting, a full shift gets you the outer of the two middle ring positions and another full shift gets you the big ring.

You can also use the inner of the two middle ring positions to allow you to access the smaller cogs from the granny ring, but that's not a good idea because it puts more tension on the chain, increasing wear. Better to shift into the middle ring. All this works as above on our Co-Mo. It's a bit dependent on drive train geometry. On my single Trek, all the rear cogs are reachable without rubbing from the outer of the two middle ring positions, but not so on the Co-Mo.

The granny/big cog combination should just barely not rub. Same with the big ring/small cog combination. You have to get the starting cable tension just right, with the FD shifter shifted all the way down. Also make absolutely sure that the shift cable end isn't hanging up inside the shifter. That happens sometimes and can drive you nuts. Pull back on the brake lever with the QR released and watch the cable end while you shift up and down as someone else spins the pedals.

I've got Race Race rings on the Co-Mo and Ultegra rings on the Trek. And all that said, I've never worked with 10-speed triples. They may be different. And as others have said, cable stretch makes absolutely no difference, other than that one must readjust as the cable stretches, as all cables do. Usually the little thumbscrew on the down tube gives enough adjustment for that.
We have an '05 C'Dale Road Tandem with an Ultegra/Truvative setup like yours. It works just like decribed above. The only problem I've had is with the barrel adjusters sometimes vibrating out of adjustment. Next time I do a cable change I'll put on different adjusters. Other than that, everything's fine. I do agree, downtube tension adjusters are better and I wish Cannondale provided them instead of barrel adjusters. But, all-in-all, we really like this bike.
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Old 07-14-07, 10:40 AM   #16
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Quote:
Originally Posted by stokessd
The fact that I'm the only one with the problem is making me feel like a moron.

I've also got a timing chain which will not stay quiet. I paraffined the chains and the drive chain is quiet as a church mouse, and the timing chain started squeaking after about 20 miles. I re-paraffined it and it did it again after another 20. I switched to white lightning and each time the chain is good for about 20 miles. The rollers on the chain are not smooth and polished, but are are scared and gouged up. I'm wondering about the inside of the links and if I've got a defective link. I really don't want to go to a wet lube. I'm going to toss that chain (with it's visible issues).

I'm also going to pick up a new front derailleur cable and see if that fixes the problem.

Sheldon
You bet! Toss that chain. You might want to invest in a Park chain wear testing tool. If you've used unsuccessful wet lubes in the past, you might want to try ProLink or Finish Line. If you don't ride in the rain, one of the Finish Line Dry Lubes will keep your chain looking good and lubed for a long time. I gave up on waxes and switched to these products.

I checked the cable routing on both my Ultegra FDs. The cable goes on the seatpost side of the raised ramp-like thingie on the end of the arm, and then along the groove in the arm. Also check the cable routing under the bottom bracket, make sure that looks good. Sometimes I'll rub a little paraffin on the cable there.
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Old 07-15-07, 11:38 AM   #17
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In our decades as tandem riders, we have found that actual 'cablestretch' occurs within about the first 500 miles with a brand new tandem/cable.
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Old 07-15-07, 12:28 PM   #18
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Of course, if you pre-stretch derailleur cables when you first install them... no worries.
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