sprocket diameters made easy for Motorized Bicycles

GoldenMotor.com

diceman2004

New Member
Aug 26, 2009
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Kitchener , Ontario
for anyone who needs to figure out the diameter of any given sprocket

simply multiply the pitch of the chain , by the number of teeth on the sprocket
then divide by 3.14

Number 35 Chain: Pitch = 3/8" | Roller diameter = 3/16" | Roller width = 3/16" | Pin diameter = 1/8" | Tensile = 2,100

Number 41 Chain: Pitch = 1/2" | Roller diameter = 5/16" | Roller width = 1/4" | Pin diameter = 1/8" | Tensile = 2,000

Number 40 Chain: Pitch = 1/2" | Roller diameter = 5/16" | Roller width = 5/16" | Pin diameter = 5/32" | Tensile = 3,700

eg: - whats the diameter of a 72 tooth sprocket , that uses number 41 chain ?
Number 41 Chain: Pitch = 1/2"
.500 x 72 = 36
36 / 3.14 = 11.464 diameter

NOTE : This is the diameter at the center of the chain roller , so you can also use this number accurately in calculations .

The outside diameter of the actual sprocket will be roughly 3/8 - 1/2 bigger at the tips of the spurs .