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Discussion Starter · #1 ·
I have a new used aluminum frame, 7700 Dura ace double front crankset & 12-27 9 speed cassette. I'm pretty sure I have all the stops, indexing, positioning dialed, but every once in a while my chain gets pulled up into the bottom chain stay when I stand up & pedal hard. It happens when I'm in my 39 up front & middle of the cogs in the back, so the chainline is reasonably straight. The front derailleur is not contacting the chain when this happens. Prehaps my chain is too long? The bike seems to otherwise shift well front & back. Never had this happen on any of my previous road bikes. Any suggestions?
 

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To set the chain length, put the rings in the big ring and the little cog. The pulleys in the rear derailleur should be right above each other. There are two other possibilities - first, you might not have the correct BB spindle length. A spindle that is too long might make it difficult to drop the chain off correctly. Also, your frame might have poor chainline. Either of these could yield the results that you are reporting.
 

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not chian length...

Chainline certainly has nothing to do with your problem. Chain length is also not the problem, if you're in the middle cogs. The link divve posted will fill you in.

Here's the correct way to evaluate chain length.

Two simple tests will determine if the chain is the correct length. First, it must not hang loose in the little ring, little cog combination. If there is no tension on the chain in the little ring, little cog combination; remove two links (one inch) at a time, until there is. When the ends of the chain are brought together, some movement of the lower pulley should occur, indicating tension is being applied. Two more links (another inch) may need to be removed, beyond the point of absolute minimum tension, to keep the chain from rubbing on itself or the chain guide tab as it passes under the upper derailleur pulley. If you want to see how much lower pulley movement will occur, without removing the extra inch of chain, shift up four teeth (11 to 15 or 12 to 16). This has the same effect as removing two links. Once this is done, the chain is set to the maximum useable length. Removing additional links will do nothing but reduce the derailleur's capacity.

Second, the chain must be long enough to avoid over-extending the rear derailleur when shifted to the big ring and biggest cog combination. If the chain is set to the maximum length as described, it should always pass this test, unless your setup exceeds the derailleur's stated wrap capacity. If you deliberately exceed the derailleur's capacity and the derailleur is over-extended in the big ring/largest cog combo, then you must either avoid that combo or add another inch and avoid using the little chainring and the smallest 3 or 4 cogs (since the chain will hang loose).
 

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NeoRetroGrouch
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farva said:
I have a new used aluminum frame, 7700 Dura ace double front crankset & 12-27 9 speed cassette. I'm pretty sure I have all the stops, indexing, positioning dialed, but every once in a while my chain gets pulled up into the bottom chain stay when I stand up & pedal hard. It happens when I'm in my 39 up front & middle of the cogs in the back, so the chainline is reasonably straight. The front derailleur is not contacting the chain when this happens. Prehaps my chain is too long? The bike seems to otherwise shift well front & back. Never had this happen on any of my previous road bikes. Any suggestions?
Chain suck is caused by the chain not releasing from the teeth at the bottom of the ring. Usually this happen while shifting under load. Do you use White Lightning or similar? I have seen one instance where a worn ring would work fine with an oil lube, but would 'suck' on every shift with White Lightning. - TF
 

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Discussion Starter · #7 ·
Wow, tons of info here, especially on the link. Thanks!

I have a 7700 double dura ace crankset with 400 miles on it, so it is fairly new. The cassette has about 1000 miles on it & the chain is about the same as the cassette. I checked the chain length per instructions you guys posted. The two rear derailluer wheels are pretty close to vertical with front in 53 / back in 12. If I remove a link, it may be too short. Bottom line, it looks pretty close, so I'm thinking this is not the problem. I keep my bike pretty clean, so I don't think a dirty drivetrain is the problem either. I do use white lightning for chain lubricant, but I have never had this problem & have been using it for the last 4-5 years? If it is causing the problem, I certainly don't mind trying something else.

From what I have read so far, I'm thinking the condition of my chain maybe the culprit. Prehaps It has a sticky link or somthing. I did transfer it from one frame to another & I had no problems with it on my old frame.

Thanks for all the replies.
 

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Do DA RDs have two positions for the tension spring? You could look at that to stiffen things up. Turn in your B screw?

A Campagnolo RD has a 'service course' spring mount so that you can run tighter tensions and avoid such circumstances.
 

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Discussion Starter · #9 ·
Spunout said:
Do DA RDs have two positions for the tension spring? You could look at that to stiffen things up. Turn in your B screw?

A Campagnolo RD has a 'service course' spring mount so that you can run tighter tensions and avoid such circumstances.
I did try turning in the B screw. Didn't make much difference. Not sure about the tension spring. As far as I know, there is not adjustments for this
 
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