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Chainring BCD

Repair & Tech Info - Bikeman Tech Info

You may notice that there are many different chainring sizes to choose from.  Figuring out what size chainring you have is pretty easy, it's just a matter of knowing what size Bolt Circle Diameter (or BCD) you have. 

A quick way to find out is to measure the distance between the center of two adjacent bolt holes then refer to the chart below to see what bolt pattern you have.



Chainring Bolt Circle Diameter (BCD)5 Bolt Chainrings

Bolt Circle
Diameter

Hole to Hole
Cntr to Cntr
56mm
32.9mm
58mm
34.3mm
94mm
55.4mm
74mm 43.5mm
110mm
64.7mm
130mm
76.4mm
135mm 79.5mm
144mm 84.6mm

4 Bolt Chainrings

58mm 41.0mm
64mm 45.3mm
68mm 48.1mm
104mm 73.6mm
112mm 79.2mm

 

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