The BCD is the diameter of the circle that passes through the center of all the bolts on your chainring. It is measured in millimeters. Knowing the BCD of your crankset is essential when choosing a new chainring for your bike. In many cases, the BCD is printed directly on the chainring, as in the example below. Sometimes, it is stamped or engraved on the back of the chainring.
If it is not indicated on your chainring, you will need to measure it, ideally with calipers. The BCD is the distance between two opposite bolts. It can be somewhat difficult to take this measurement if you don't have calipers, as the crank arm can get in the way.
There are symmetrical and asymmetrical chainrings. The drawing below illustrates both types of chainrings, and the table shows the measurements corresponding to each type of BCD.
| BCD | Distance (mm) | Distance (in) |
| 94mm | 66.5mm | 2.62in |
| 96mm - Symétrique | 67.9mm | 2.67in |
| 96mm - Asymétrique | 55.2mm; 78.8mm | 2.17in, 3.10in |
| 104mm | 73.5mm | 2.90in |
There are other types of BCD (102, 110, 120, etc.), but we do not currently offer compatible chainrings.
Chainrings can also be mounted in Direct Mount.
The Pilo interfaces are referenced below. We recommend mounting the chainrings with the original screws provided with your crankset.
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Questions? Contact us contact@soshanger.ca !