Cutting a chain to length

[Tom]

I vaguely remember being told that an easy way to cut a chain to the right length is put it on the big ring, the big cog, thread it through the pulleys and line it up so the pulleys are stacked vertically. That's your length. Did I remember right?

[BdaGhisallo]

I think it's big ring / small cog. If you think about it, if you cut it to get the pulleys vertical in the big ring and big cog, there's no way a normal road derr will have enough wrap capacity to eliminate slack in the small ring / small cog combo.

Another way is the big ring / big cog but make sure there is an extra link or two more than would render the chain taut in the combo, with no derr wrap.

[woolly]

The Park Tool website is usually a pretty good source of information for stuff like this: http://www.parktool.com/repair/readhowto.asp?id=26

Enjoy. :beer:

[FierteTi52]

Another way is the big ring / big cog but make sure there is an extra link or two more than would render the chain taut in the combo, with no derr wrap.
I use the method above. Big to big and skip the derailleur with a 2 link overlap. This gives you the shortest chain possible but allows for a big to big combo without tearing the derailleur off the bike.
Jeff

[Dave]

Two 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 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).

[rdparadise]

And line up a new chain next to the old one and then cut to length.

Bob

[BoulderGeek]

Wow, I must be over-simplifying.

I just put it in big-big combination and determine how much to remove to put the deraillieur pulley cage at a 50-degree angle.

Usually it is 4 links, and I am done.

[RPS]

As Dave suggested above, I also maximize chain length by measuring on the small-ring and small-cog. That gives me the greatest flexibility to change cassettes if needed while being able to use all gears.

Interestingly, the bike shop that built my custom tandem didn't maximize the chain length, and I wasn't able to use a 12-27 safely until I replaced the chain. :crap:

[musgravecycles]

atmo a longer chain is better than a shorter chain.

less driveline friction
lasts longer

campagnolo's method yields a longer chain than the shimano method...

[Dave]

Wow, I must be over-simplifying.

I just put it in big-big combination and determine how much to remove to put the deraillieur pulley cage at a 50-degree angle.

Usually it is 4 links, and I am done.

The big-big method not only involves eyeballing the cage angle, it's only good for the cassette used when the length is determined. Set it with an 11-23, then later change to a 12-27 for a hilly route and the chain will be 1 inch too short.

The little/little method makes the chain the correct length for any cassette.

[FierteTi52]

The big-big method not only involves eyeballing the cage angle, it's only good for the cassette used when the length is determined. Set it with an 11-23, then later change to a 12-27 for a hilly route and the chain will be 1 inch too short.

The little/little method makes the chain the correct length for any cassette.
I'm running a 12-27 cassette with a compact 34-50 crank. The chain wrap exceeds the capacity of my standard DA rear Derailleur. Therefore, the big to big plus 2 links is the way I do it. Yes the chain is slack on the small cog small chainring, but it's better than tearing off a rear derailleur. By using the big ring while on the lower portion of the cassette like you should, all is fine anyhow.
Jeff

[Jeff N.]

Little-little. Remove just enough links that allows the chain to move freely and unbindingly though the rear derailleur. Jeff N.

[Jeff Weir]

Little-little. Remove just enough links that allows the chain to move freely and unbindingly though the rear derailleur. Jeff N.


That is exactly what a person who shall go un-named told me atmo.