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Discussion Starter · #1 ·
I've just replaced my chain, and eyeballed it to the best of my ability the correct chain length, judging from both my old chain, as well as what "looks right", after consulting Sheldon Brown's site.

So i have a few pics, and a few corresponding questions:





When on the Small/Small cog combination, i get my chain flapping around, the derailleur unable to take up all of the slack. The incoming chain to the derailleur is not in line with the tension cog, and "chatters", as it tries to skip up onto the tension cog, but can't, because of the too severe alignment difference.

So, is this "normal", as in, i shouldn't shift into this combination? I don't see this as a problem, but i do like clarification.




When on the large/large combination, I'm unsure if this is the correct length. I've matched it as close as i could with the original chain, perhaps a link longer. I would think this combination also shouldn't be used, as the misalignment is too great. And the rear sprocket keeps hopping from 1st to 2nd, due to the front chain ring pulling it down the cluster.

So, all this boils down to: Does this look right?
 

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Bike Addiction
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763 Posts
That is what they call cross chaining. Its bad for chains and thangs. Wears them out. Might be a little rough on your rear derailleur too if you stay there too long. I think I have a couple less links in mine.
Edit: I was refering to the last 2 pics. You can see the cross effect in the last pic.
 

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R.I.P. DogFriend
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You need to shorten up the chain enough so the derailleur cage doesn't double back on itself like it does in the pic with the chain on the small chainring/smallest cog... just barely. Should work fine then. When it's in the big chainring/biggest cog, the derailleur cage will be almost horizontal, but you don't ride very far (if at all) in that combo.
 

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You want the chain long enough to go around the largest cog and largest ring and then have 2 links extra. Even though large to large is cross-chaining and should not be used when riding, this is the standard method of determining chain length.

As explained at ParkTool:

Chain Sizing - Largest Cog and Largest Chainring Method
An alternative method for determining chain length for new chains is to use the largest size sprockets on the bike. It is easiest to size the chain without threading it through the derailleur.

Shift the front derailleur over the largest chainring, and the rear derailleur on the smallest cog.
Thread the new chain through the front derailleur. It is not necessary to thread the chain through the rear derailleur at this point. Simply wrap the chain around the largest front chainring and around the largest rear cog.
Pull the chain tight, and note the closest rivet where the two could be joined. Keep in mind a chain can only be joined by mating inner and outer plates.
From the closet rivet, lengthen the chain by counting over an additional two rivets (two links), which is a distance of one-inch. Cut the chain at this point.
Remove the chain from the bike and thread it through both derailleurs and join the ends.
 
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