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Can you comment on chain lenght?

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Can you comment on chain lenght?

Old 10-30-09, 08:26 AM
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Can you comment on chain lenght?

I got Ultegra CN-6700 10-speed Chain, length 116 links, my cassette is 11-23 and cranks 53-39T, chain stay is 16in.

Chain was initially too long:

My tests with 116 links:

1. Largest chain ring and largest sprocket combo (Big/Big)– works fine with all 116 links
2. Smallest chain ring and smallest sprocket combo (Small/Small) – I have so much chain extra I could wrap around my ankles and play in Alcatraz movie.

I did my Google research and found lot of opinions\suggestions\chain calculators even. It seems that all of those guys\companies are using different naming conventions and rules to cut the chain.

Shimano Test (Big/Small): Ultegra 6700 docs says to check the angle, but this is pretty hard to check/determine, 4-5 links do not really change this angle much.



In the search for minimum length:

I choose empirical approach and fount out that I could remove minimum 4 links for test # 2 to work (smallest chain ring/smallest sprocket)

Minimum: at test 2 (small/small)
After removing 4 links rear derailleur moves just a bit to make the tension in combo 2, this setup works, but there is little tension. If I set the chain to 3 links chain is too lose no tension at all, so with 4 it is absolute minimum to create some tension, I’m afraid that chain will be hitting stay when going on some rough roads (I would not be in that gear ratio anyway, but …. theoretically I could) When I remove 5 links chain has a bit more tension and feels much better.

Minimum at test 1 (Big/Big)
When I remove 5 links and switch to test 1, (biggest chain ring/biggest sprocket) derailleur looks quite expanded, there is chain “bend” as many describes but I’m not sure if I’m not stretching it, When I stretch it really hard, I would be still able to remove one more link for total of 6, but that would be absolute maximum and there would be no “bend” in chain.

As you can see I’m at maximum or minimum of one link depending on test 1 or test 2

What is your experience, better make it tight, or loose it up a bit? Is it better to be close to max/min on upper end or lower end?

Here are pictures of my rear derailleur, I removed 5 links. Did I cut my chain to short or it is long enough:

Can you post picture of your derailleur in one of those setups? I can't sleep since yesterday


Pictures of 3 different tests:


Test 2 combo (small/small):








Test 1 combo (Big/Big)








Shimano Test (Big/Small)





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Old 10-30-09, 08:32 AM
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You are making this way more complicated than it should be.

I just use the Big-Big+2 approach, which actually comes recommended with a lot of the chain instructions as well as the components that you buy (KMC, SRAM). Works every time, all the time...
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Old 10-30-09, 08:35 AM
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Old 10-30-09, 08:36 AM
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Back in the day that last test was the norm, and there was some thought to making the chain a touch longer, so that there was less tension (even some hang) in the small x small combinations....lower friction, less loss of power, better climbing....that was the idea, not sure it really worked that way, but it was the cool thing to do.

A more modern approach is to run the chain big x big, bypassing the derailleur to estimate minimum chain length, then add two links.....works like a charm on my SRAM drivechain...

Last edited by MarkSch; 10-30-09 at 08:37 AM. Reason: slow typing
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Old 10-30-09, 08:40 AM
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If you don't plan on using a different cassette with this chain, size it by wrapping it around the largest cog and largest chainring, without running it through the rear derailleur, find the shortest point where the chain could be connected, and add one inch. Break the chain at that point and connect it (after running it through the derailleurs of course), and you're done.

You will have enough chain to cover big/big (which is the THE most important element of chain sizing, because of the catastrophic damage that can occur if the chain is too short for this combo), and with the drivetrain you're running your RD will take up the chain slack no matter which gear combo you're in.

Currently, it sounds like your chain is too long, the derailleur can't take up all the slack in some combos-

Here's Sheldon's writeup on the subject; he, of course, says it best. And he has pics:
https://www.sheldonbrown.com/derailer...ent.html#chain

Last edited by well biked; 10-30-09 at 08:45 AM.
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Old 10-30-09, 08:54 AM
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Lots of words for a simple thing.

Lots of people go big-big but that's really only great for when you don't plan on changing your gearing much.


You are running compact. Go small-small and make sure the chain is short enough to have the bottom pulley on the RD go back so far that it will cause the chain to rub on the RD cage.

If you have done that then you are running the longest chain you can safely run. Then you can run any normal setup with any cassette (essentially).
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Old 10-30-09, 09:18 AM
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Originally Posted by well biked
If you don't plan on using a different cassette with this chain, size it by wrapping it around the largest cog and largest chainring, without running it through the rear derailleur,
Currently, it sounds like your chain is too long,
I was concerned it is too short because in Big/big combo, RD looks “stretched”, but I guess as long as it changes the gears it is all good.

https://zebase.com/bikes/BigBig2.jpg
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Old 10-30-09, 09:22 AM
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Originally Posted by Psimet2001
Lots of words for a simple thing.
Sorry for the length of initial post,
I just want to clarify; all pictures posted are of the same chain after removing 5c. from the chain, I was especially concerned about RD in big/big

https://zebase.com/bikes/BigBig2.jpg

But since it works it is good I guess.

My Small/Small looks like this now:

https://zebase.com/bikes/smallsmall2.jpg
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Old 10-30-09, 09:25 AM
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You chain length looks fine from the pictures, but next time, start with a chain that is 1 inch longer and see if it hangs loose or rubs the RD cage in the little/little. If it does, then the chain is too long and the length you have now is as good as you can get.

Also keep in mind that a chain can only be changed in length by 1 inch or two-link increments. You can't remove 3 or 5 links and still join a chain.

I always use the little/little method because I never use a RD with insuffcient wrap capacity and that method insures the maximum chain wrap from any RD. That length will also handle any cassette within the RD's wrap capacity and never need to change the chain length.

Last edited by DaveSSS; 10-30-09 at 10:02 AM.
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Old 10-30-09, 09:45 AM
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Originally Posted by sebo2000
2. Smallest chain ring and smallest sprocket combo (Small/Small) – I have so much chain extra I could wrap around my ankles and play in Alcatraz movie.
After looking at your pic, I don't see what you mean. It appears the derailleur is taking up the slack just fine in the small/small combo, which is all you can ask for.
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Old 10-30-09, 10:38 AM
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Originally Posted by well biked
After looking at your pic, I don't see what you mean. It appears the derailleur is taking up the slack just fine in the small/small combo, which is all you can ask for.
I was concerned about Big/Big combo and how RD is extended, but I think it was overreaction from my side
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Old 10-30-09, 12:30 PM
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Originally Posted by Psimet2001
You are running compact.
The OP's cranks are 53/39
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Old 10-30-09, 01:13 PM
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Originally Posted by well biked
The OP's cranks are 53/39
I see that in his text....but I was looking at the pictures....and those look like a compact. Hard to tell seeing as how the pictures were taken from the *wrong* side and all.

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Old 10-30-09, 02:04 PM
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Pictures are taken from the “good” side, it was intentional. I should just say:
Look at my RD in 3 different settings:

Big/big,
Small/small
Big/small

And tell me by looking at the RD is the chain is not too short.
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Old 10-30-09, 02:13 PM
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Hard to tell through a wheel

I never work on a bike from the wrong side....

- btw it looks fine. and trim that cable.
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Old 10-30-09, 02:23 PM
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Me, I would add an inch of chain to get to what psimet is striving for in post #6.

That way you could change to a 25 rear w/o issue if you thought you needed it that day.
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Old 10-30-09, 02:41 PM
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for the future

if you're taking pictures with the intent of asking for drivetrain help

take pictures from the drive-side of the bike.
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Old 10-30-09, 03:49 PM
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Disclaimer - just having fun....


I found your problems:



A. Cassette is too clean. You have never ridden this bike. That or it's just computer generated....

B. Excess cable is weighing down the derail making it appear to be more extended than it really is...

C. That valve cap and retaining nut are going to cause a massive un-balance on your trainer and cause the carbon fiber stays to explode.

....just sayin.
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Old 10-30-09, 07:33 PM
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Originally Posted by Psimet2001
Disclaimer - just having fun....
I found your problems:
A. Cassette is too clean. You have never ridden this bike. That or it's just computer generated....
B. Excess cable is weighing down the derail making it appear to be more extended than it really is...
C. That valve cap and retaining nut are going to cause a massive un-balance on your trainer and cause the carbon fiber stays to explode.
....just sayin.
hehehe

No Disclaimers necessary, I do not sue that easily. Cramer’s lawyer said: we do not have a case.e,

A. Yes, this is virtual product of my imagination; I do not intend to ride it in the real world other than on home trainer. That is why “Orange” tire.
B. I want to use that extra cable as a whip when riding on the virtual trainer, I will be whipping all the bad car drivers like Indiana Jones. To justify the weights I will ride without left shoe.
C. It was to create the bounce effect of Toronto bad roads, my concerns about stays were the same, I will remove it or change for titanium


BTW you have a good eye, this whip should be invisible so they can’t see me…
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