How do I find the right adapter size for my bike?

First, determine which rotor size you want to use. Then, you need to find out the brake mount size of your fork or frame. The easiest way to find this information is on the manufacturer’s product page under “Specifications.” The difference between the rotor size and the brake mount size gives you the size of the required adapter. For example: 203 mm – 180 mm = 23 mm.