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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 12-15-07, 08:17 PM   #1
hearncst
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Ft shifting problem

My wife and I have a 2007 cannondale with an ultegra front deraillier. It will up shift ( to a larger chain ring) using shifting cable tension, and downshift ( to a smaller chain ring) with derailier spring pressure. Our problem, it won't downshift into granny gear with any pressure on the pedals. If we're on a 3% grade and then round a corner and face a steeper pitch, we are unable to down shift. Our older burley did not have this problem. Any possible solutions? Is there a triple that downshifts under pressure (tension) and up shifts with a spring. Our local pro level bike shop hasn't been able to help.
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Old 12-15-07, 10:18 PM   #2
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Maybe the derailleur isn't moving quite far enough in to change it to the grannie.Back the "low or L"screw a bit.Not too much or the chain will go past the grannie and off.
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Old 12-16-07, 08:31 AM   #3
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Originally Posted by hearncst View Post
Our local pro level bike shop hasn't been able to help.
Given that you've been riding tandems and understand the need to unload the pedals to shift into your alpine gear, I'm a bit puzzled given that a good mechanic couldn't resolve the issue as I don't believe there is anything fundamentally different about the triple on your C'dale from any other triple on a bike aside from the wider rear axle spacing.

Regardless, and even though a pro bike shop looked at it, if you do some of your own mechanical work I'd recommend revisiting the installation instructions from Shimano and comparing them to how your front derailleur is installed and set-up:

http://techdocs.shimano.com/media/te...9830616213.pdf

Park Tools also has a very good on-line set-up guide:
http://www.parktool.com/repair/readhowto.asp?id=75

Sometimes it's just the little details like cage alignment that can throw it all off.
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Old 12-16-07, 12:32 PM   #4
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No, it's more like the spring doesn't have enough power to deflect the chain when the chain is under tension.
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Old 12-16-07, 02:17 PM   #5
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Originally Posted by hearncst View Post
No, it's more like the spring doesn't have enough power to deflect the chain when the chain is under tension.
Have you checked your derailleur cable to make sure that it's not dragging or binding?
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Old 12-16-07, 02:24 PM   #6
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Another thing is the middle ring may not be a middle ring, i.e. it may be missing the cutouts to allow the chain to move off to its inside. I bought a new middle ring for our tandem and realized after that it was a "small ring for a double", not a "middle ring for a triple". So it's sitting in my parts box for now.

I used to file down teeth (1 almost all the way, 2 about half way) to "ramp" unramped chainrings. You might be able to do the same thing to assist the chain.

An easy way to tell is if it has pick up pins on the inside. If it does, it's meant to be a middle. If it doesn't, it's meant to be a small.

I am not next to our Cannondale tandem but if the seat tube is round and of reasonable diameter, you can put on a "chain watcher" or some other device to prevent the chain from dropping off the small ring (I prefer N-Gear's metal thing to the standard chain watcher). Then adjust the derailleur to overshift by a lot and rely on the watcher to keep the chain on the ring. Unfortunately if the derailleur is toward its inner limits, the spring tension is not substantial.

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Old 12-18-07, 10:36 AM   #7
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Lots of good suggestions here! One other thing to think about is whether or not you are trying to shift from a badly crossed chain position. If the chain is on an outer cog on the cassette this might be the problem. Try already being shifted to an inner cog before you go to the granny. You'll probably want some combination like that anyway if you need the granny.

Rick

Quote:
Originally Posted by hearncst View Post
My wife and I have a 2007 cannondale with an ultegra front deraillier. It will up shift ( to a larger chain ring) using shifting cable tension, and downshift ( to a smaller chain ring) with derailier spring pressure. Our problem, it won't downshift into granny gear with any pressure on the pedals. If we're on a 3% grade and then round a corner and face a steeper pitch, we are unable to down shift. Our older burley did not have this problem. Any possible solutions? Is there a triple that downshifts under pressure (tension) and up shifts with a spring. Our local pro level bike shop hasn't been able to help.
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Old 12-20-07, 05:51 PM   #8
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One more idea to think about, we bought a KHS that had the same problem it would shift on the stand but not on the road. The deraillier was hitting the seat tube, if that's the problem you need to install a spacer on the right side of the bottom bracket. Just my two cents.
Seth
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Old 12-23-07, 04:04 PM   #9
dubbelop
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Quote:
Originally Posted by carpediemracing View Post
Another thing is the middle ring may not be a middle ring, i.e. it may be missing the cutouts to allow the chain to move off to its inside. I bought a new middle ring for our tandem and realized after that it was a "small ring for a double", not a "middle ring for a triple". So it's sitting in my parts box for now.

I used to file down teeth (1 almost all the way, 2 about half way) to "ramp" unramped chainrings. You might be able to do the same thing to assist the chain.

An easy way to tell is if it has pick up pins on the inside. If it does, it's meant to be a middle. If it doesn't, it's meant to be a small.
Boy, how did people ever shift in the days before pins/ramps/cut away teeth and the lot?
FWIW: we have TA rings on both tandems (one of which is a Cannondale RT with Ultegra front mech) and they up- and downshift just fine.

Quote:
Originally Posted by carpediemracing View Post
I am not next to our Cannondale tandem but if the seat tube is round and of reasonable diameter, you can put on a "chain watcher" or some other device to prevent the chain from dropping off the small ring (I prefer N-Gear's metal thing to the standard chain watcher). Then adjust the derailleur to overshift by a lot and rely on the watcher to keep the chain on the ring. Unfortunately if the derailleur is toward its inner limits, the spring tension is not substantial.
cdr
Yes, the N-Gear fits a Road Tandem: we actually have one on ours (an 04 model).
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