Single chain length for multiple setups (chainrings and casettes)

Discuss light weight issues concerning road bikes & parts.
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mike001100
Posts: 97
Joined: Sun Dec 04, 2016 10:26 am

by mike001100

Hi,

I would like to run the following:

52/36 chainrings
50/34 chainrings

12-25 casette
11-25 casette
11-28 casette

in all combinations :)

Can someone please help me regarding chain length? If I use a calculator, it comes out as:

50/34 and 11-25 (smallest combo): 52 links
52/28 and 11-28 (biggest combo): 54 links

So, what do I size to? I'm guessing biggest (54 links) or somewhere in-between, i.e. 53 links?

Thank you :)

kode54
Posts: 1187
Joined: Tue May 23, 2006 9:39 pm

by kode54

sounds right. split the difference like you did.
- AX Lightness Vial EVO D + DA9150 + Enve SES 3.4 carbon hubs
- Parlee Altum + DA9150 + Enve SES 4.5 carbon hubs
- Parlee ESX + DA9150 + THM SRM PM + Enve SES 6.7 CK hubs
- Independent Fabrication Ti FLW + DA9100 + Enve 3.4 CK hubs

ooo
Posts: 528
Joined: Sat May 21, 2016 12:59 pm

by ooo

use longest
'

TobinHatesYou
Posts: 1208
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Your max gear difference is 35t.

Official capacities:
SRAM short cage and Shimano (SS) short cage = 33t
Dura-Ace R9100 = 35t
SRAM WiFli and 6800/5800 (GS) medium cage = 37t
R8000/R7000 (GS) medium cage = 39t

Every short cage derailleur I've used has been able to handle 35t unofficially. Just make your chain as long as it can possibly be in 34x11 without touching itself at the top pulley wheel. This should leave you plenty of buffer for when you run 52x28. Also what derailleur are you using.

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Rick
Posts: 2032
Joined: Sat Aug 29, 2009 4:30 pm

by Rick

I use the "small-small method": Put your chain on the smallest ring in front and the smallest cog in rear.
Then adjust chain length so it as long as possible while the jockey pulley is still able to keep enough tension such that the chain still clears the upper jockey pulley (which will then be close to the chain when the lower jockey pully is rotated back and up, taking out the chain slack.0 (If you NEVER crosschain, you could use the second-smallest cog).

Using this method your derailleur will be handle its largest capacity cog in the rear, and usually a bit bigger than officially specified.
Last edited by Rick on Sun May 20, 2018 4:42 pm, edited 1 time in total.

1415chris
Posts: 1084
Joined: Sat Apr 18, 2009 8:59 am
Location: Surrey UK

by 1415chris

Unless you will be giving these cassets more less equal mileage, l would rotate them with the chains.
From length standpoint always go for safe shortest possible, running chain outside of derailleur on big chainring and biggest sprocket and adding one full link.
If you end up with the slack (very unlikely on 52/28), there is nothing you can do about it. If the chain is too short, attempting big/biggest combo something's gotta give, chain or derailleur.

2lo8
Posts: 413
Joined: Thu Mar 31, 2016 10:32 am

by 2lo8

There's a lot of contradictory advice here, so I guess I'll give my input even though parts of it have already been mentioned in other posts.

Running the same chain on two different cassettes will accelerate wear on cassettes. Cassettes normally wear slower than chains, and using a worn shain on a new cassette can also lead to shifting problems. Some people rotate chains like so:
New cassette > A > B > C > A > B > C > A > B > C > New cassette
because it gets longer cassette life since in this example (actual ratios may vary, people who mostly use a couple of small cogs will find it difficult to have a chain that shifts both the worn and unworn cogs well), the chain is wearing about 3 times as fast as the cassettes, so light wear is put on the cassette and chains A, B, and C, then medium wear for all of them, and so on. Attempting to use the same chain on different cassettes is the opposite of this. Chains never unstretch (wear for pedants), teeth don't restore themselves to be like new. Usually parts will have accelerated wear from not meshing well until they match the wear level.

That being said, chain swaps add time to your maintenance routine. If you have the money to replace consumables, this is really not an issue and convenience is most important.

Assuming you don't swap chainrings and never use a cog smaller than 11t, small-small with always give you the largest range of full cassette compatibility for your given chainstay, chainrings and chainlength. Small-small gives you the longest chain your drivetrain can handle. If you have 50/34 and 11-32 and 11-23, 34x11 is small-small for both. Obviously changing the small ring or the smallest cog will change small-small. Running a small-small chain will get you less chain tension than big-big sizing, possibly saving you a tiny fraction of a watt from jockeys, more chainlinks to wear and resulting in slightly worse chain retention and chain slap and a few extra grams from extra links.

This advice does not apply if you are choosing to exceed the published gear capacities of your drivetrain, in which case the chain should always be sized for the biggest ring and biggest cog you will ever use with it. It is always better to have a slack hanging chain in small-small than have your RD ripped off and trashing your drivetrain and frame and killing you in the process from attempting to shift big-big when the chain is not long enough.
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Rick
Posts: 2032
Joined: Sat Aug 29, 2009 4:30 pm

by Rick

My method:
I switch wheels and cassettes a lot, so I don't want to have to change chains every time. Also, chains are a lot cheaper than cassettes.
So get a good chain-wear indicator tool (I have a couple, but I usually use the Park) and make sure you have a new chain ready to go at 0.5% stretch, and replace it as soon as it hits 0.7% stretch.
Using this method I have been using the same cassettes for years and swapping back and forth with no negative effects. The cassettes usually become obsolete or get replaced for other reasons before I have any chain-skip.
Wait till you find a good sale somewhere on ultegra-level chains and stockpile a few!

mike001100
Posts: 97
Joined: Sun Dec 04, 2016 10:26 am

by mike001100

Thank you all,

I don't think I will be going down the "multiple chains" route, I change wheels way too often and don't like quick links...

In the end, I sized the chain to 54 links, i.e. one more than I need now (measured in effect for a 28 tooth cassette), but I will probably be staying with 25 at the rear and just getting a compact chainset... so I'll remove the extra link :)

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