Chain Ring Sizes
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.
 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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