Chain length calculator

Sierratim

Well-Known Member
Over the years I've modified gearing on most of my bikes. What to do about the existing chain was always an issue; longer, shorter, who knew until you could wrap it around the biggest cog and front ring. So considering another change I (finally) did the obvious and Googled 'chain length calculator'. Some don't work correctly, some reference the tried and true method I've always done, and others didn't have enough tooth count range in the calculator.

But THIS ONE seems to meet all my needs. For my current setup (48t chain ring, 42t biggest cog, and 478mm chain stay) it correctly calculates the chain at 120 links. For the 46t cog I'm considering it calculates a 122 link chain. For a 50t cog I'd need to go with a 124 link chain, both doable with the replacement 126 link chain I have in the shop. Nice to know.

Unfortunately the 50t cog would require changing the medium cage derailleur to a long cage. More studying...😎

BTW - My bike is a hard tail. For a FS frame you would need to additional links to these calculated results.
 
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Gionnirocket

Well-Known Member
Good to know you had positive results.
Since I'm playing around with my drive train at the moment, I may just see what results I get.
Bookmark'd
 

Stefan Mikes

Well-Known Member
What is the "Center Distance", @Sierratim? The chain stay length?

With 48t chainring, 46t rear sprocket, standard 1/4 in chain pitch and 478 mm chain-stay length (18.818 in) I got a completely wrong result...

1601101493818.png
 
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Gionnirocket

Well-Known Member
I haven't tried it yet...
But after looking up what chain stay length is 🙃 . . . That's what I assumed as well.
 

Stefan Mikes

Well-Known Member
OK. Let us correct the data. The chain pitch is 1/2" or 12.7 mm.
1601116410135.png


122 links?! Come on, my Vado needs 132 links. Something wrong with the calculator or with me...

This chain length calculator could be better but it handles neither long chainstays nor large rear sprockets...

No reliable chain length calculator that I could find. Park Tool give this rigorous formula:
1601116863670.png

where:
F - number of chainring teeth
R - number f the largest cassette sprocket teeth
C - chainstay length in inches.

Here, Excel calculation:
1601117440140.png


The formula gives 124 links.

How comes my Vado needs 132 links?! I can prove it...
 
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Stefan Mikes

Well-Known Member
In my opinion, all these calculators are good for nothing. I'm lucky the shop mechanic who was replacing the chain and the cassette in my Vado in May did the chain fitting properly himself, so now I just need to remember: 132 links for Vado!

With Giant Trance E+ (never mind the technical specs), the Park Tool formula suggests 122 links and that's about right. The stock chain came with 124 links, and we found there were 2 links too many there.
 

Sierratim

Well-Known Member
OK. Let us correct the data. The chain pitch is 1/2" or 12.7 mm.
View attachment 66597

122 links?! Come on, my Vado needs 132 links. Something wrong with the calculator or with me...

This chain length calculator could be better but it handles neither long chainstays nor large rear sprockets...

No reliable chain length calculator that I could find. Park Tool give this rigorous formula:
View attachment 66598
where:
F - number of chainring teeth
R - number f the largest cassette sprocket teeth
C - chainstay length in inches.

Here, Excel calculation:
View attachment 66599

The formula gives 124 links.

How comes my Vado needs 132 links?! I can prove it...
This calculator does not take into account the derailleur cage length. Mine is a Shimano XT GS, a medium cage. Stephan with your 46t cassette you may have a longer cage derailleur, but 132 links does seem long to me.

I think this calculator is useful to determine what chain length you might need with a gear change. Without it I'm just guessing. It tells me that I all ready have the 126 link chain I need for the changes to my Vado i'm considering.

There's still no substitute for wraping your new chain around your biggest chain ring and biggest cog, adding 2 or more links, and cutting the chain to length. More if you ride with long cages and FS bikes. I'll do this when my new cassete and derailleur cage frame gets here, before cutting my chain...😀
 

Sierratim

Well-Known Member
Holy complicated stuff batman! Can't we just follow Park's video? Does this work? I'm about to change cogs.

Works great, esp if you have rolls of chain stock like our LBS or a dozen or more of a wide range of sizes and lengths like our local Bicycle Kitchen. For the rest of us changing gearing, how do you know what chain length to order? A decent (read complicated) calculator helps me order the right length chain with my new components.

I ordered my new components today based on my preferred calculator. I'll let you know how it works out, or not!...🤣

BTW - my ebike currently uses a 120 link chain. My changes are calculated to need 126 links. We'll see.
 

Stefan Mikes

Well-Known Member
Is this what yours is doing with 132 links?
No, Tim. It is what Trance E+ does with the stock 124-link chain (as installed at the factory). The proper size is 122.

Regarding the Vado, it has the SGS cage because of the 46t sprocket. I'm really glad I ordered the full drive-train servicing of my Vado in May (that was when the Vado electronics were overhauled to TCD-W). As I wrote earlier in our Club thread, the shop mechanic was irritated because he discovered late it should be the 11-46t cassette as per spec (not the 11-42t one) and then he found a long chain was necessary (he had to order the E8000, 138L from their warehouse). All the pain was with the guy, and he did very nice chain fitting: That's why I know the 132 links is the perfect size for that very special Vado...
 

Gionnirocket

Well-Known Member
No, Tim. It is what Trance E+ does with the stock 124-link chain (as installed at the factory). The proper size is 122.

Regarding the Vado, it has the SGS cage because of the 46t sprocket. I'm really glad I ordered the full drive-train servicing of my Vado in May (that was when the Vado electronics were overhauled to TCD-W). As I wrote earlier in our Club thread, the shop mechanic was irritated because he discovered late it should be the 11-46t cassette as per spec (not the 11-42t one) and then he found a long chain was necessary (he had to order the E8000, 138L from their warehouse). All the pain was with the guy, and he did very nice chain fitting: That's why I know the 132 links is the perfect size for that very special Vado...

Mistakes are made everywhere, everyday... even at the manufacturer.
Were you experiencing any problems with the Vado using 124 links that are now resolved with the 122 links