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Chain length ?...(10 posts)

Chain length ?...dawg
Apr 16, 2002 2:30 PM
I installed my first new chain and am concerned that it seems too short. Following the directions in the Zinn manual, I placed the chain in the large chainring and smallest cog (running the chain through the rear der) and measured 1 link overlap. The problem is that when I am in the large chainring and one of the larger cogs, the rear der is pulled very far forward, almost horizontal. I had not noticed this before. Is this ok?
re: Chain length ?...Spoke Wrench
Apr 16, 2002 2:39 PM
If it will shift into the big/big combination and out again, I wouldn't worry about it. That's a combination that you don't use in real life anyway.
you are supposed to do thatAlexx
Apr 16, 2002 5:07 PM
..in the LARGE RING/LARGE COG gear, then add 1 link. Yes, your chain is too short, and you are probably going to break a tooth!
re: Chain length ?...Ken of Fresno
Apr 16, 2002 5:11 PM
I use that method for my mtb because the gear ratios are much wider, but for road bikes there's another method that may work better. Put the chain in the large chainwheel and small cassette cog combination. The correct chain length would cause both derailer pulleys to line up with a single line perpendicular to the ground. This is how my road bikes are, and they shift fine.

Best of luck,
Ken
that's what i did...dawg
Apr 16, 2002 5:38 PM
In the large chain ring-small cog combo it is perpendicular. When shifting to the larger cogs, the pulleys are pulled forward, nearly horizontal.
Are you sure?Ken of Fresno
Apr 16, 2002 6:21 PM
According to your post, you said you put the chain in the large chainwheel and smallest cog and measured 1 link overlap. If you did that, I don't know how you could even shif off the small cog. Don't mean to parse words, but I'm not familiar with the Zinn manual. What is the largest cog on your cassette? I have a 25 and have no problem shifting onto it.

Best of luck,
Ken
Can we back up a minute?Spoke Wrench
Apr 17, 2002 5:47 AM
What we are looking for is the shortest chain that will shift smoothly into and out of the big/big gear combination. When you find that, your derailleur will be nearly horizontal. That's how it is supposed to look in that combination.

If your chain is too short, by even a tiny amount, the chain will be too tight in this combination and will not shift smoothly and will make "popping" noises. If this is your situation, you will have to lenghten your chain by one full inch because that's the least amount you can do.

A lot of confusion comes from the definition of "one link." If you use the Park Tool instructions but substitute the words "one inch" for "one link" everything will work out perfectly.
re: Chain length ?...Len J
Apr 17, 2002 4:37 AM
Check out the park site:

http://www.parktool.com/repair_help/FAQchainlength.shtml

They recommend Big ring, Big cog (Without threading through the rear der.) plus two links.

They also have pictures of what a too short chain looks like. Sounds like what you are describing.

Len
agree with Len--check Park site vs. Zinn books,...JS Haiku Shop
Apr 17, 2002 5:31 AM
had same problem (cranks wouldn't even turn with just one extra link in the big/big), checked park's site, they said 2 links did it, works fine now. good luck.
try this...C-40
Apr 17, 2002 6:10 PM
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 as it passes under the upper derailleur pulley. 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. It won't help keep the chain from skipping or jumping.

Second, the chain must be long enough to avoid overextending 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 capacity.
If you want to see how much lower pulley movement will occur, without removing the extra two links, shift up four teeth (11 to 15 or 12 to 16). This has the same effect as removing two links.