Chain length?

[Skyward]

I’m getting new chain rings, cassette, and chain. How do I measure the correct chain length?

[meehs]

Originally posted by Skyward
I’m getting new chain rings, cassette, and chain. How do I measure the correct chain length?

Here's how I do it and I really don't know if this is the best way:

Thread the chain through through the derailleurs and wrap it around the big chainring and the largest rear cog. Pull the chain tight until the rear derailleur cage is at 45 degrees. Mark the link that gives you the 45 degrees and splice the chain together at that point. If you can't get exactly 45 degrees, I always go to the next tighter link, since you're not supposed to be using the big ring/big cog combonation anyway.

[boudreaux]

Originally posted by Skyward
I’m getting new chain rings, cassette, and chain. How do I measure the correct chain length? Check the repair section at www.parktool.com The quick dirty way is to put the chain on big ring and big cog in the rear,not thru the derailer,pull tight and then add 1"(2 links). That works for the particular big cog being used,but is you were later to switch to a bigger cog the chain could need to be lengthened. There are other methods that will allow enough chain length to accomodate any cog that is within your RDs capacity spec for both large cog and chain wrap.

[jstraw]

Hmm...I thought the correct length was determined when your deraileur pulleys were vertical with a big ring/small cog combo...

[boudreaux]

Originally posted by jstraw
Hmm...I thought the correct length was determined when your deraileur pulleys were vertical with a big ring/small cog combo... There are lots of different ways to do it. Has to be long enough to acomodate the big/big, as well as have no slack when in the small/small. Knowing what you are doing and why is the important part.

[meehs]

Originally posted by jstraw
Hmm...I thought the correct length was determined when your deraileur pulleys were vertical with a big ring/small cog combo...

I'm sure that'd probably work fine and provide more flexibilty for future cog changes (like the method that boudreaux described). Like I said, I don't know if my method is the best way to go. I think the method that I use is supposed to achieve the shortest chain length possibe. The theory being that a shorter chain = crisper shifting and less weight. Of course you could probably make-up the weight difference of two chain links by farting before you ride...

[davidbod]

Originally posted by meehs
I'm sure that'd probably work fine and provide more flexibilty for future cog changes (like the method that boudreaux described). Like I said, I don't know if my method is the best way to go. I think the method that I use is supposed to achieve the shortest chain length possibe. The theory being that a shorter chain = crisper shifting and less weight. Of course you could probably make-up the weight difference of two chain links by farting before you ride...

I disagree, farting would not do it, but pissing on the nearest bush would.

[jstraw]

I know how to set up a drive train to shift properly. I got my chain-lenght method from Lennard Zinn and it works perfectly so I haven't had a need to experiment with other methods of determining length.

[boudreaux]

Originally posted by jstraw
I know how to set up a drive train to shift properly. I got my chain-lenght method from Lennard Zinn and it works perfectly so I haven't had a need to experiment with other methods of determining length. If it handles the big/big and does not drag on the RD when in the small/ small, than it is right at least for that combnation of big chainring/big cog. There is more than one way to do it.