So I'm in the midst spacing my rear wheel on my sportster. I've tried searching for threads like this but couldn't find anything quite as specific as this. I have the tire centered and the right side spacer pvc mock up in place. Here's my problem. I know that the caliper has to be directly center on the rotor. I know the spacer between the caliper and the bearing is pretty crucial. How do I go about finding the measurement of that spacer?