Chainsuck on brand new Di2 9070 Venge Boonen Ltd build

Discuss light weight issues concerning road bikes & parts.
ghisallo2003
Posts: 593
Joined: Mon Jan 02, 2006 7:10 pm

by ghisallo2003

Small ring, small cog. Mech must have tension with clean chainline and sufficient gap between chain and jockey wheel / cage.

by Weenie


xclemjustinx
Posts: 10
Joined: Mon Jun 10, 2013 9:28 pm

by xclemjustinx

^incorrect way to setup your bike for the correct chain length

ghisallo2003
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Joined: Mon Jan 02, 2006 7:10 pm

by ghisallo2003

Try reading campag manual: 10-15mm gap at small; small to set length.

If you dont have tension and chain touches jockey wheel then you surely do have a chain that is too long.

xclemjustinx
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Joined: Mon Jun 10, 2013 9:28 pm

by xclemjustinx

That's not a campy chain and that's not a campy bike.

ghisallo2003
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by ghisallo2003

Yes thats right, my mistake, It probably works in a completely different way.

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Calnago
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by Calnago

Doesn't matter if it's campy or not. Principle is the same. Like @ghisallo2003 said, "If you dont have tension and chain touches jockey wheel then you surely do have a chain that is too long".

Just from looking at the picture, it seems that dropping the chain down to the smallest cog would create a situation where the derailleur is not providing any tension on the chain. Very easy to check.

However, the things @thisisatest suggests would probably be a more likely cause for the chain suck, particularly as it relates to the interface of the crank spider and chainrings. I'd check all that VERY carefully... the chain's gotta be catching somewhere, and it doesn't take much.
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maxxevv
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Joined: Wed Feb 09, 2005 4:51 am

by maxxevv

xclemjustinx wrote:How can you determine if his chain is too long or too short from that picture? In order to see if his chain is the correct length you must put it in the big chainring and the smallest cog in the rear and see if the pulley wheels are 90 degrees of one another.


Its just a guideline that will work with some but NOT all chainring and cogset combinations. It will work well with a standard 39/53 and 12-25 setup. BUT ... try doing it on a 36/52 and 11-28 setup and you get into problems ...

You still need the "small-small" combination check for sufficient chain tension and the "big-big" combination check to check for sufficient chain length (and prevent unnecessary strain on the RD at extreme crossover) to be 100% sure.

If you've wrenched enough bikes ( be it hobby or as a job), you'll see all sorts of funny permutations and their quirks. Most of the people here are making a judgement call based on our own experiences. And why not you wait for the original poster to come back to verify our prognosis instead ??

Andrew69
Posts: 142
Joined: Thu Feb 19, 2009 10:52 am

by Andrew69

ryker wrote:^Yeah check your chain length!

That chain looks waaay too long!
Half way down the cassette and the jockey wheels are already close.

Beautiful bike btw!

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tommasini
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by tommasini

Agree with many others - a failure by the shop to properly pick the proper chain length......

5 8 5
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Joined: Sat Jul 29, 2006 2:36 am
Location: UK

by 5 8 5

xclemjustinx wrote:^incorrect way to setup your bike for the correct chain length

Using the small / small method means you've got the longest possible chain. It allows you to use a bigger 1st gear cassette (within reason) without having to lengthen or change the chain.

Geoff
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by Geoff

How else can you do it? :noidea:

mjduct
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Joined: Tue Dec 27, 2011 2:19 pm

by mjduct

xclemjustinx wrote:^incorrect way to setup your bike for the correct chain length



According to who?

Thats pretty much the tried and true way for initial setup, Then you check it on the big-big combination and make sure your derailleur span it without getting sucked up in your cassette.

xclemjustinx
Posts: 10
Joined: Mon Jun 10, 2013 9:28 pm

by xclemjustinx

5 8 5 wrote:
xclemjustinx wrote:^incorrect way to setup your bike for the correct chain length

Using the small / small method means you've got the longest possible chain. It allows you to use a bigger 1st gear cassette (within reason) without having to lengthen or change the chain.



What if your rd can only handle a 28 tooth and you just gave the chain the longest possible length? Now what. Having the chain to long can decrease shifting efficiency and can have issues of the chain dropping. The standard is big big without going through the rd pulleys and add one set of links.

xclemjustinx
Posts: 10
Joined: Mon Jun 10, 2013 9:28 pm

by xclemjustinx

maxxevv wrote:
xclemjustinx wrote:How can you determine if his chain is too long or too short from that picture? In order to see if his chain is the correct length you must put it in the big chainring and the smallest cog in the rear and see if the pulley wheels are 90 degrees of one another.


Its just a guideline that will work with some but NOT all chainring and cogset combinations. It will work well with a standard 39/53 and 12-25 setup. BUT ... try doing it on a 36/52 and 11-28 setup and you get into problems ...

You still need the "small-small" combination check for sufficient chain tension and the "big-big" combination check to check for sufficient chain length (and prevent unnecessary strain on the RD at extreme crossover) to be 100% sure.

If you've wrenched enough bikes ( be it hobby or as a job), you'll see all sorts of funny permutations and their quirks. Most of the people here are making a judgement call based on our own experiences. And why not you wait for the original poster to come back to verify our prognosis instead ??


I've wrenched more bikes the you can fathom and don't give me that "I've been a bike shop owner for 40 years so I know everything attitude."

A standard road bike setup will have the pulleys at a 90 degree of one another. If you are using a MTB then the application is different. I've worked on so many bikes where the chain length was incorrect and the shifting was horrible. Take a look at the installation instructions from Shimano regarding chain install.

http://techdocs.shimano.com/media/techd ... 700387.pdf

by Weenie


5 8 5
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Joined: Sat Jul 29, 2006 2:36 am
Location: UK

by 5 8 5

xclemjustinx, I don't think you get it!

The chain wouldn't be too long, the RD would still wrap the chain.

There isn't an exact / correct chain length - it's a range. That range will function perfectly well.

What happens when the pulleys aren't perfectly vertical when using big / small. Does one "remove" a pair of links or "add" a pair. It's not the exact science that you make it out to be.

Big / big and small / small are accepted methods for chain length. Like maxxevv I use both methods erring towards the longer chain.
Last edited by 5 8 5 on Wed Jun 12, 2013 5:39 pm, edited 1 time in total.

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