Chain Pitch:
Chain pitch is the difference between a chain's two adjoining links. Similarly, Sprockets also have a pitch which is the distance between their two adjoining teeth.
Have a look here:
http://www.ekchain.com/jis.htm
Let's take a Chain pitch number:
.428 as an example.
Here, the 1st digit 'x', is the pitch/ distance between 2 links, in terms of 'x/8 inch'.
So, a .428 chain belongs to
"4" pitch series, and has a 4/8 or 1/2 inch pitch. (x=4)
The next 2 numbers (like
"28") denote the sprocket width/ fatness which the chain will comply with too, in terms of distance between inner plates.
A chain ending in ‘20’ measures around 6.35mm between the plates.
If the number ends in ‘28’, the dimension is around 7.94mm.
If the number ends in ‘30’ or ‘32’, the width is around 9.53mm.
Because wider chains are typically stronger as well, the 2nd & 3rd digits also indicate a chain’s strength, relative to other chains with the same pitch.
See the image below for clarification:
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In your Bikes: Remember, your entire setup (both sprockets and chain) HAVE TO be on the same chain pitch. You can't fit a .520 pitch sprocket(s) on a .428 chain, or vice versa.
For example: If you choose .428 pitch for your bikes, your chain and both the sprockets should be .428 only.