How to Measure Chain Length

[Kato]

Looking to see if anyone can help me with the chain length needed for a 1942 CWC / Roadmaster.
I found 2 of them - identical original owner bikes. I've already finished the 1st one and am working on the 2nd now.
It doesn't have a chain so I need to get one. I took string and ran it around the chain on the first bike until the ends met up.

Looks like 60" - 62" or so Does that sound right - my way of measuring right.....?
If I just go from front edge of front sprocket to back edge of rear it's more like 52"
I found a 71" chain with a master link - can I shorten it to make it work.

Any help / info appreciated !!
Thanks
Mike

 

[c.p.odom]

Careful there is math involved.

 

[Kato]

Careful there is math involved.

And the math involved is...........?

 

[c.p.odom]

There are a number of equations for bike/motorcycle chain lengths (non-derailleur).
This is the simplest: L = 2 (C) + (F/4 + R/4 + 1)
L = Chain length in inches. Round the final result to closest whole inch figure.
C = Chain stay length in inches, measure to closest 1/8”. Use chart below to find decimal measurement.
F= Number of teeth on largest front chainring.
R= Number of teeth on largest rear cog.

 

[Mark Davo]

Any bike shop should be able to shorten your chain. Better yet, a friend that has and fixes his own old bikes). I have several CW skiptooth boys bikes, and it seems that 56 link (inc. the master link), seems to be a common size.

 

[patman73]

if both bikes are the same take off the chain from the one wit a chain & measure it bu counting the links ad or subtract links on new chain as needed to tighting it up to where you what you wheel in the drop out , if that dont work try a bike shop
hope this helps

 

[Kato]

Thanks for the info all........