Tandem Cycling - shifting problems-front derailleur
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Recently I replaced the front derailleur cable on my 2004 cannondale road tandem (ulterga STI levers, shimano 105 fd) . Now when I wish to down shift from the big ring to the middle ring, I have a lot of resistance. Because of the resistanceI have to use a lot of force to down shift. This results in me skipping the second ring and dropping down to the smallest one. I then have to up shift. Of course, all this makes my stoker very unhappy!
It has something to do with cable tension. If I disconnect the cable from the front derailleur and just pull slightly, the ulterga shifter has no resistance and shifts normally. I tried to use a slacker cable, but this causes other problems in shifting.
Any help would be greatly appreciated. I have not had much luck using the normal cannondale e-mail address…funny as I own several of their bikes.
Debica Poland via Spokane Washington
04-25-05, 11:11 AM
Appropriate tension on the cable can be critical. Also, check that new cable moves freely in the cablehousing . . .
04-25-05, 11:16 AM
You should never have to force the shifter. Sounds like a kink in the cable or housing someplace. Also, check where the cable goes under both BB's to make sure it is not hung up on something or not in the guides.
Thanks for the reply.
1) the cable is moving freely, it is a high quality stainless steel cable in the original shimano casing. I added some Teflon lube.
2) It has something to do with the tension. If the cable is a bit loose it down shifts fine, however I can’t up shift very well as it doesn't have the pull. I tried all kinds of tricks to no avail
3) Is there an alternative cable routing perhaps?
04-25-05, 11:23 AM
Very odd....I don't see why there would be resistance, supposed to be the other way around.
Does it up-shift smoothly? Or is it just a one-way problem.
Is it catching on something? A snag or a kink?
Are the cables running through the guides on the bottom bracket reversed?
Hope this helps, I admit I am guessing.
04-25-05, 11:28 AM
Try backing off the high limit screw about 1/8 turn. Sometimes if the limit screw is just a touch too tight cable tension puts the derailleur in a bind at that point. The result is greater than normal shift effort followed by a violent shift that often over shoots the middle ring.
04-25-05, 11:53 AM
Based on your description of the problem I concur with RG's assessment: You can probably reduce the tension by:
1. Doing as RG suggestes and backing out the upper (high) limit screw to allow the FD cage to travel out a bit further, OR
2. Reducing tension on the FD derailleur cable by turning the barrel adjuster clockwise a 1/2 turn or so at the upper cable stop on your downtube, OR
3. Letting the derailleur cable out an additional 1mm to 2mm in the FD's pinch bolt to reduce the tension on the shifter's ratchet mechanism.
Like any ratchet mechanism, there needs to be a little play to allow the ratchet's pawl to disengage from the ratchet teeth. Apparently, all of the play was eliminated during your cable adjustment, either by happenstance from where you fixed the cable end into the FD pinch bolt or perhaps due to an adjustment of the upper cable stop when dialing in the FD movement.
I liken this to that brief moment of panic that sets in when you have inadvertently parked your car or truck with the front wheels cocked against a curb or parking stop and, once the power steering in your car lost power, the steering column locks up hard against the integrated locking mechanism that keeps your steering wheel from turning once you remove the keys. Panic sets in when you get back in the car and attempt to turn your ignition key, only to find that the key won't turn... as the ratcheting mechanism is locked by the tension on the steering column. Only when you physically turn the steering wheel to release the tension will the ratchet release and allow you to turn the ignition key.
I seem to have the same problem when changing down but it only occurs when I change gears on the accent of hill and the gears are under pressure during the climb. I find what works well if I tell the stocker to ease off slightly and the change is much smoother - only takes a split second of easing off.
Mdk and the 555 EXPRESS (Enthusiastic Xtreme Paired Riders Experiencing Simultaneous Speeds)
I'm sure you've done this, but:
Have you properly set the indexing? The STI shifters have four detents separated by three clicks. One is for the big ring, two are for the middle ring, and one is for the small ring. I like Mark's and RG's explanations better, but I also wonder if you are trying to get by with using the inner three detents across the three chainrings.
I normally install a new cable by shifting onto the small ring, leaving the barrel adjuster a little toward the short end, and pulling fairly hard on the end of the cable as I tighten the clamp screw. It is then ususally a simple matter to shift up and down and likely take up some tension with the barrel adjuster, to get things just right.
It usually seems like I need to set the indexing with STI so a little bit of overshift is needed to get the chain to jump up on the big ring, and as I stop pressing and let the lever sit on the detent, I have the perfect index setting to prevent rub on any cog except the inside one, with the big ring.
Thanks all for the great tips. I used all of them, including readjusting the set screw just a bit and ever so slightly loosening the cable. It seems to work. Although the shifting is not as crisp as on other triples on single bikes…
04-27-05, 11:33 AM
Although the shifting is not as crisp as on other triples on single bikes…
That's what happens when you add 3' of derailleur cable and lose control over 1/2 of the power production...
Actually, there is a "trick" for improving front derailleur shifts on tandems and 'mdk555' hinted at it. Rather than regurgitating it all here, let me provide you with a link to a previous post from '03 where I discuss some of the nuances associated with getting smoother shifts from your tandem's front derailleur (first part of the response): http://www.bikeforums.net/showpost.php?p=229865&postcount=9
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